Used primarily in scrollin gthrough games. Some of the words explaining LOD Bias are found below:

LOD bias affects the point at which mipmapping levels change. Increasing values for LOD bias makes the overall images blurrier or smoother. Decreasing values make the overall images sharper. Some textures look better if they are very sharp, other look better blurred.

LOD Bias essentially compensates for textures that would otherwise be under or over sampled. Mipmapped textures can be made sharper with a negative bias or blurrier with a positive bias. Unfortunately, by increasing the LOD (with a negative value), aliasing artifacts and texture shimmering in the distances is exacerbated such that it is virtually unbearable at the most detailed settings. The effect is not illustrated too well with screenshots, but it is very obvious as you are moving through the game.

Hope this was of assistance!