Common names: Dilate, Grow, Expand
Dilation is one of the two basic operations in mathematical morphology (the other being erosion). The effect is to enlarge the boundaries of regions of foreground pixels. Thus areas of foreground pixels grow in size while holes (background) within these regions become smaller. Dilation is the dual of Erosion.
The kernel is a mask used as follows. For binary images, for every 1 in the kernel the image pixels are ORed. For grey scale images the MAXimum of the image pixels is taken where the kernel is 1.