two or more sheets of material together and you get a laminate, which is essentially just a material made up of layers. Since the layers are usually different materials, laminates are examples of composites
though the materials aren't integrated together in the same way as with other (matrix) composites. It's also important to remember that a laminate isn't simply several layers of materials: the materials have to be permanently bonded together with something like adhesive, so they behave as one material, not several. You can think of the adhesive (or adhesives—because there might be more than one) as an additional material in a laminate.
Generally, because a material you'd normally use by itself (say paper, wood, or glass) isn't strong or durable enough to survive by itself. Paper isn't waterproof, for example, while plastic is relatively hard to print on. But what if you print on the paper then coat it with plastic? The laminated composite material you've made gives you the best of both worlds.