Very simply, lenticular refers to a sheet of plastic lens (that can come in different sizes and thickness) consisting of an array of optical elements called lenticules that create a convex perspective of multiple images. This technology is used to create a lenticular image. When viewed from different angles, different areas under the lens are reflected to the viewer. Views are arranged under the lens so that each eye is projected a different view. The brain then processes these views to a single coherent 3D, Flip or Animated image.

Lenticular technology actually dates back to the 1690s when Gois-Clair, a French painter, discovered that he could achieve a dimensional effect on canvas by interposing a grid between a viewer and a painting. Gois-Clair painted two distinct pictures on a plane surface, over which he affixed a grid of vertical laths. These laths were arranged perpendicular to the plane and attached to it at right angles. By looking at the painting from the left side, one would see one painting; another distinct painting could be seen from the right side, and a combination of the two paintings could be seen when looking at the painting straight on.

Lenticular is array of cylindrical lens

Lenticular lens job is to focus light on the print from different angles. A good example would be a pair of eyeglasses. They correct the vision by focusing light onto the eye.