Compressed two-channel (RG) texture format.
BC5 format compresses textures to 8 bits per pixel, keeping only the red and green color channels. It is widely supported on PC and console platforms.
It is a good format to compress two-channel textures, e.g. as a compression format for tangent space normal maps or velocity fields. For one channel textures, see BC4.
Additional resources: Texture2D.format, texture assets.