Bilinear can refer to bilinear filtering or bilinear interpolation. Bilinear filtering is a method used to smooth out when they are displayed larger or smaller than they actually are. Bilinear filtering uses points to perform bilinear interpolation. This is done by interpolating between the four pixels nearest to the point that best represents that pixel (usually in the middle or upper left of the pixel).

Bilinear Interpolation: This resampling method assigns the average digital number (DN) of the four pixels closest to the input pixel (in a 2x2 window) to the corresponding output pixel. The mathematical function is bilinear.