Duo is the official mascot of Duolingo. It is a green owl of an unknown species and is meant to symbolize knowledge, wisdom and learning. In Duolingo it can at times serve as a coach to motivate users to achieve higher learning goals, and can also instruct users on several aspects of the Duolingo website.
Duolingo's mascot wears several outfits in different occasions. It sometimes wears an academic gown, a coach Outfit, or a hat. You can buy outfits for Duo on the iOS or Android lingot store.