Anisotropic filtering level of the Texture.
Anisotropic filtering makes Textures look better when viewed at a shallow angle, but comes at a performance cost in the graphics hardware.
Usually you use it on floor, ground or road Textures to make them look better.
The value range of this variable goes from 1 to 9, where 1 equals no filtering applied and 9 equals full filtering applied. As the value gets bigger, the Texture is clearer at shallow angles. Lower values mean the Texture will be more blurry at shallow angles.
Direct3D 11 API has a limitation where using anisotropic filtering enables trilinear filtering. Other graphics APIs don't have this limitation and allow selecting filtering modes and anisotropic level independantly.
See Also: Texture assets.