An example of a game asset is one of the Rings of Power in a Lord of the Rings video game—but it could also be the character who wears the ring, the texture layer on the ring that makes it shiny, the sound that plays when the ring goes on, and the animation of a character putting on the ring.
A game asset is any deliverable content item for a video game, including 3D models, textures, animations, and sounds.