A lenticular is a two-dimensional image that changes based on viewing angle.
A computer program cuts multiple pictures into fine slices and interlaces them together into one image. When a lenticular lens is placed over the image and properly aligned, it bends light to focus on different parts of the image depending on the angle of the viewer. The result is seeing a different image depending on where you are in relation to the artwork.
diagram of how it works
Lenticulars have often been used in advertising, but I’ve recently been playing with the process a great deal for my own art.