PowerOfTwo
From polycount
"Power of 2" means the numbers 2, 4, 8, 16, 32, 64, 128, 256, 512, etc. Also called pow2 or n2.
Usually this is used to describe the Texture sizes that a game engine requires in order to make good use of video Memory. An example pow2 texture size would be 32x64.
A texture that is not powers of 2 (e.g. 33x24) may be simply loaded into graphics memory as-is (on modern hardware), or it has to be padded up to the next pow2 size (to work with texture compression), or the game engine may stop with an error message that it needs to be fixed.