A piece of plastic that has a prism like structure to it is attached to the surface of the picture. The plastic refracts different lines of the image depending on what angle you view it from. Later, as the technology improved, it started to be used for displaying 3D images. After all, the two eyes of the viewer are looking at the picture from slightly different angles anyway, so why not show a stereo pair of pictures. Lenticular images have been around since the 1940s and were first mass produced by a company called Variview.
Lenticular images are also usually clearer and more defined than holograms.
One of the exciting things about lenticular displays is that real-time computer generated lenticular video is now possible. Instead of having a static picture behind the lenticular screen, we have a hi resolution liquid crystal display. Its fairly simple to alter a game or other piece of software to render the scene twice and interleave the two images together before displaying them on a screen. With any luck this technology will be noticed by the big industry giants and we will see lenticular displays being available to the average Joe within the next few years.