Odahviing is a dragon and was an ally of and right-hand dragon to Alduin. The Dragonborn must summon him to an encounter in Whiterun during the main quest. At which point he is captured and bargains for his freedom, swearing his loyalty to the Dragonborn, and taking them too where they can find and confront Alduin.

In the dragon language his name is spelled using the words for Snow/OD, Hunter/AH, and Wing/VIING but some write it as (Winged Snow Hunter).

At some point during the story Odahviing and other dragons loyal to Alduin began to have doubts about Alduin's rule, likely out of fear of losing another war. Which was likely the catalyst to him betraying Alduin to the Dragonborn. After Alduin defeat, he chooses to go his own way and embrace his newfound freedom while swearing his loyalty to the Dragonborn. He does however refuse to restrain himself in the same way as Paarthurnax does, calling his "way of the voice" a form of tyranny.
odahving