Graphics and video
Anisotropic filtering is a type of texture filtering which increases the visual quality of textures at steep angles to the camera, such as those that recede into the distance.
The option to enable anisotropic filtering is present in almost every PC game on the market today. Usually you will be able to select texture sample rates of 2x, 4x, 8x, or 16x. The texture sample rate is the number of passes the anisotropic filtering algorithm makes on the current textures in the frame. Most newer GPUs can render settings of 8x or 16x AF without a noticeable loss of performance, but if you are experiencing low FPS, lowering the sample rate or disabling the anisotropic filtering setting may increase performance.
Due to how linear texture filtering works, the need for anisotropic filtering is reduced as the rendering resolution is increased. Despite this, it is still recommended to enable the maximum viable anisotropic filtering setting due to the noticeable improvement in texture clarity.
Most modern 3D games provides native AF. It can be configured through its Graphics settings, console commands, launcher options, or configuration files.
If a game...
...there is a method to 'override' game's default texture filtering. Depending on your system's graphics type, below are methods in forcing Anisotropic filtering:
Anisotropic Filtering article on Wikipedia