A Wyvern is similar to a dragon, however with a few key differences. They lack front legs and support the front of their bodies with their clawed wings. They usually lack the ability to breathe fire and are far faster than dragons due to their smaller size and more slender bodies.
technically skyrim's dragons are whatever the fuck the universe designer wants them to be. They could call them goats and you would have no right to say they aren't as you didn't write the universe.
Also no they aren't technically wyverns as wyverns cannot breath fire.
I still remember one time me and my brothers was playing D&D and we were all in this alley when a bunch of guys jumped off of roofs into the alley to fight us. And my 2nd oldest brother was the DM and he was telling us how many guys were there and where they were. Than he rolled for another guy to jump down and he looks at the dice a 1 and says "He was the new guy. Let's just say he landed wrong."
Also no they aren't technically wyverns as wyverns cannot breath fire.