Dragons start out basically as big lizards, but get more powerful and more intelligent the older they get. This trend never reverses - dragons only get more powerful with age. Note that these 'brackets' are by rough power / intelligence levels. Normal dragokind will vary from the above brackets by 25%.
Dragonkind are really rare. Extrapolating the map to the size of the whole world, there are maybe 10 - 15 Wyrms on the planet. Which is probably a good thing, because it pretty much takes divine intervention to kill one (or another Wyrm). There are probably about 5 times that number of Dragon (i.e. 50 - 75 globally). Wyrms spend most of their time 'asleep', and are pretty much legendary.
Drakes and smaller don't get much press.
Dragons are sexed. However, they are solitary and territorial by nature, and a mating is a very delicate thing. As such, dragon pairings are rare. Dragons reach sexual maturity during the Drake phase of life, but most Drakes do not mate successfully, due to lack of "social skills" (this will be explained below).
When a dragon pair mates, the female carries the eggs for a gestation period of somewhat over a year (about 14 months). During the later phase of this period, she is too heavy to fly - usually the male protects and provides for her during this time. At the end of this period, the female lays a clutch of 4 to 12 eggs..

Eggs:
Dragon eggs are 2 - 4 feet long and egg-shaped. Their shells are thick and leathery, and harden to brittleness as the eggs mature. About 8 months after laying, the hatchlings break through the brittle shell with a bone spike on the end of their nose. During the maturation period of the eggs, the mother remains protectively awake, and hunts often, to regain her energies after the production of the eggs. The father dragon will remain nearby, but will leave to return to his lair from time to time. These departures become more frequent and more prolonged as the eggs mature.

Hatchling (0 -4 years):
Hatchling dragons are walking appetites. The mother dragon increases her hunting to feed them. Dragons are carnivores - the mother will pre-chew meat for the youngest hatchlings, but by 6 months they can eat for themselves. The father dragon will occasionally help in the hunt, but the pair's territorial instincts begin to re-emerge during this time, and eventually the father will simply return to his own territor.
Hatchlings begin as 2.5 to 4-foot winged lizards, and grow to 5 to 10 feet in length before leaving their mother's lair. Generally the time they learn to fly is the same as when they leave the lair. Hatchlings are unintelligent - basically they are walking mouths and will attempt to eat anything that vaugely resembles food. 10% of all dragons die as hatchlings, for one reason or another.

Dragonet (4 - 30 years):
A hatchling becomes a dragonet when it leaves its mother's lair. This is the most vulnerable time for dragonkind. The dragon leaves its mother's lair and learns to hunt on its own. For a year or two, dragonets may stay in their mother's territory, and she may even assist them somewhat, but the dragonet will eventually establish a territory of its own. Usually such a territory is a few square miles - enough to support the dragonet's ravenous appetite.
Dragonets range from 7 to 30 feet in length. During this phase of their existence, they learn to master their own bodies - learning to fly, swim, and so forth. Their intelligence grows from that of a hatchling to that of a cunning predator. 55% of all dragon-kind die as Dragonets.

Drake (30 - 200 years):
When a dragonet has fully mastered its flying and hunting skills, and its intelligence has reached the level of a wolf or fox, then it begins to expand its territory beyond what is needed to supply it with food. When this occurs, the dragon has become a Drake. Drakes physical growth is slow, but they develop mental faculties during this time. Drakes learn to reason, and begin to plan. They start displaying typical draconic emotions such as greed, curiosity, or rage. As a drake gets older, it will discover language, and develop the complex mental facilites to handle this. Drakes will begin to "play with" their prey, capturing and studying animals. This especially applies to intelligent prey, such as humanoids - most drakes will eventually learn a language from a captured humanoid. Of course, this tends to enrage other humanoids, and many drakes die because of this. A drake is powerful enough that not much else can kill it - although many fall in territorial combat with other drakes (and full dragons will kill those stupid enough to challenge them) and the odd drake will die to a unicorn, wyvern, gryphon, or other magical beast.
Physically, drakes are 20 - 80 feet in length. Older drakes are fully as intelligent as humans, but endowed with greater patience, cunning, and savagery, albeit less control over their emotions. Drakes are highly territorial - while physically mature, drakes have great difficulty overcoming their territorial instincts to mate. And when such a mating does occur, the male generally does not support the female during her time of vulnerability. In the exceptionally rare circumstance that a drake lays a clutch of eggs, the female is usually not mature enough to sucessfully raise her brood - she generally abandons her hatchlings to die.
A drake will eventually stake out a sizeable territory with a lair near the center. The drake will take pains to protect the lair and may begin to accumulate posessions there. Eventually the drake will come to the notice of other Dragons and, if it does not get itself killed by challenging one of them, the Drake will be accepted into the community of Dragons. Of course, over a third of all dragon-kind die during this phase, leaving less than 1% or so who make it to become full Dragons.

Dragon (200 -?1000? years):
When a Drake is accepted into the community of Dragons, and taught the secret and ancient Draconic tounge, it becomes a full Dragon. Dragons develop and pursue their own special interests, and most become quite involved in the world. Often, a Dragon will move its lair to an optimal site for its particular pursuits. Each Dragon is highly individual in nature, and they vary considerably.
There are a few things that Dragons share in common: they all learn to use magic, they are all active in the world, and they all develop at least one magical means to use their breath as a long-range weapon. All are far more intelligent than all but the most exceptional humanoids. Dragons range from 60 to 300 feet in length, although this seems to depend more on the individual than on age.
Almost nothing can kill a Dragon. Another Dragon, perhaps, or the greatest of humanoid heroes. Some kill themselves in magical experiments gone awry.

Wyrm (?1000? - ???? years):
The final phase of the draconic lifecycle. As a Dragon gets older, it loses interest in its worldly pursuits. It begins to spend more time in deep contemplation, and in sleep-like trances. Eventually, it abandons its worldly lair and finds a remote place to drift through the years. Wyrms have no lair or hoard, although they retain huge territories. However, Wyrms can sleep for decades at a time, and really don't care about what happens in the world. They spend their time in magical/philosophical contemplation of things far beyond the realm of mortal kin. Wyrms are all huge, 200 - 300 feet in length. They don't fly often, as it seems a strain for their vast bulk. They are vastly intelligent, beyond the reach of even the greatest of elves. In magic, they are powerful enough to rival the gods. So on and so forth. Essentially, nothing can kill a Wyrm. Unless it wants to die, of course.

Draconian Population (General):
Dragons are essentially a solitary species. I intend to list by name all the dragons in "Europe", along with descriptions, histories, and so on. Here's a quick start, by name and location. Again, these are hard facts - no humanoid would know more than half of this.

Wyrms (note that these names are maybe 5-10% the length of the real name):
Iyeiskjadryllja - Polar Scandinavian Ice-Wyrm.
Sahara - Deep Saharran desert. Hey, it's her desert.
Pumoch-tannal - Bottom of the Black Sea. (the only Wyrm actually on the map.)

Dragons:
Gibraltar - It's his rock. He charges a steep toll to use his strait.
Syssiphus - Lairs on a cloud. Usually located over NE France, but has been known to travel.
Scourge - Big, dumb, firebreathing. Terrorizes orc country (northern Ukraine)
Daksdraudangas - Swiss Alps

Draconian Population (Profiles):
Name: Ijeskaldyr
Alternative names: Iyeiskjadryllja, Ijeiskjadryllaron, Ilenskaldar, etc.
Other References ('Nicknames'): Wyrm of The North, Ice-Wyrm, Grandfather of Dragons, The Ancient One, The Polar Wyrm, The Frozen One. (Note on Names: Ijeskaldyr is so incredibly ancient and so powerfult that there are literally hundreds of variations on his name or different labels he has been referenced by. Since it would be pointless to attempt a comprehensive listing, I have just listed some of the more common ones here.)
Age: The oldest living thing on the planet, according to Elvish and Draconic lore. Ancient elven records list him as being "old in his power, long before the Changing". When the world was first formed, he arrived already at Wyrm status.
Power Level: Equivalent to most gods. Certainly far more powerful than any other non-divine being on the planet, all other Wyrms included.
Physique: Solid white, with ice-blue eyes. Average to lean build. 170 meters long, 150 meter wingspan (although recorded tales list him anywhere from 100m to 5 miles in length).
Activity level: No confirmed sightings in the past several centuries (most of Folk "recorded history"). He's buried under the permanent ice-sheet in northern Scandinavia. His last several periods of activity were quite minor - a quick flight to stretch the wings, some light snacks, and back to the ice sheets. Last serious activity was over 1000 years ago - only the elves might actually remember.
Reference in folklore and legend: There are hundreds of references in ancient lore - most species have at least one reference to this great being. The most notable is his role in Giant lore - the awakening of the Polar Wyrm is one of the great signs of the coming of the end of the world (compare to the role of the Midgard Serpent in Ragnarok). Even southern races, such as the Tagur, have legends of the Grandfather of Dragons.
Abilities / Magic notes: Ijeskaldyr has ultimate power over cold. He is most comfortable at sub-zero temperatures.
Personality: Asleep. It would actually be very difficult to disturb him - most humanoids he could easily be rid of without even waking up. His mind has wandered off to the other mental planes that dragons explore, and has been there for centuries. Ijeskaldyr is unlikely to wake up any time soon, but should someone awaken him, they will certainly face his fury. However, he is wise beyond the ages and knows more than any mortal could even dream of.