Dragons - The Elder Scrolls V: Skyrim wiki

Dragons are a large and powerful race from Akavir that were once very widespread throughout Tamriel. Although seeming rather beast-like, they are very intelligent and capable of language; their language can be used to cast powerful magic usable by a Dragonborn, but some dragons can speak other languages. Most dragons have been rendered almost extinct. However, dragons have recently resurfaced in Skyrim. There are six known races of dragon, unless you have the add-on of Dawnguard which increases to eight: black, frost, blood, elder, ancient, skeleton, revered and legendary dragons.

Dragon Gameplay Behavior

Although most commonly hostile, occasionally dragons will fly around you as if you're not there. Dragons will catch sight of something they wish to attack. Not all dragons may be hostile towards the player, Some dragons may be docile and harmless unless provoked.

Dragons may fly by you any time randomly. They will sometimes gang up on you in packs as you progress in skill and in the storyline.

Their combative patterns usually involve flyovers while shouting spells, hovering while shouting at you, and ground attacks. The sheer force of their landing can crush the ground around them. Ground attacks involve swinging their tails, using shouts, and attempting to bite with their jaws. If dragons successfully do enough damage to a player they can produce a finishing move by grabing half of the players body into their mouth, swinging them back and forth a couple of times, then lunching them in the air like a ragdoll.

Dragons will not land exclusively on open ground. They have been known to perch on buildings, cliffs, and rocky outcrops to gain a tactical advantage over the player.

Types:

• Dragons - These are considered to be on the lowest rung though can provide a challenge for players early in the game.
• Blood Dragons - These seem to vary in color and appearance. They can breathe both fire and frost and are slightly tougher than the normal "dragons".
• Frost Dragons - They are the same as basic dragons, but breath frost instead. They are typically colored white and grey.
• Elder Dragons - These are golden scaled dragons that are significantly tougher than the previous types both in melee and breath attacks. They can breathe both fire and frost.
• Ancient Dragons - Aside from Alduin himself, these are the deadliest dragons in Skyrim with dark brownish scales and capable of breathing either fire or frost. They also have exceptionally damaging melee attacks making them remarkably deadly both in the air and on the ground.
• Revered Dragons - These are tougher and more resilient to taking damage and exclusively breathe fire. Their scales are orange with blue dorsal markings, and have long, wide, flat tails and bodies. They begin to appear throughout Skyrim at level 59.
• Legendary Dragons are one of the many breeds of Dragons found in Tamriel. They are the most powerful Dragon sub-type known to exist in-game. Unlike other breeds of Dragon, Legendary Dragons have distinctive thick, curved horns. They have a black and purple scale color. They are also unique in having what appear to be compound eyes, formed of four "eyes" in a single socket.

(Credit for this" types" list goes to the The Elder Scrolls wikia andUnofficial Elderscrolls Pages wiki)