Buzz Lightyear is a real person. That’s the set-up for Lightyear, the 26th feature-length effort from Pixar.
A teaser for the new film has been released, showing a more restrained graphic approach than usual for the studio. The human characters in Lightyear presumably exist in the same universe as the human characters in the Toy Story series, and they appear stylized to around that same degree.
From what we understand, Lightyear recounts the fictional story of the real person who inspired the Buzz Lightyear toy. So, the character in this teaser is not the Buzz Lightyear of previous Toy Story films, but an entirely new character.