Defines the anisotropic filtering level of the Texture.
Anisotropic filtering makes Textures look better when viewed at a shallow angle, but it can be slower to process on the GPU. Anisotropic filtering is commonly used to improve the appearance of floor, ground or road Textures.
The value range of this variable is 0 to 16. A value of 1 equals no filtering applied and 16 equals full filtering applied. As the value gets bigger, the Texture is clearer at shallow angles. Lower values mean the Texture is more blurry at shallow angles.
When the anisoLevel value is 0 and in Quality Settings, Anisotropic Filtering is set to Forced On, Unity does not apply anisotropic filtering. You can use this to disable anisotropic filtering for a Texture that would behave unpredictably with anisotropic filtering applied.
When the anisoLevel value is between 1 and 9, and in Quality Settings, Anisotropic Filtering is set to Forced On, Unity sets the anisoLevel to 9. If the value is higher than 9, Unity clamps it between 9 and 16.
If you use the Metal, Vulkan and OpenGL APIs, you can control mipmap filtering and anisotropic filtering levels independently. When you enable anisotropic filtering in any other graphics APIs, Unity also enables trilinear filtering.
Additional resources: Texture assets.