Here's a good introductory video about porcelain veneers. The procedure is not cheap and usually requires filing the natural teeth down somewhat in order to provide the best aesthetic fit for the veneers. Temporary veneers are installed first to see if all is okay with the shape, color and size. After this test drive of a couple of weeks the lab fabricated porcelain veneers are bonded on top of the natural teeth using lasers and other lights.
Porcelain veneers can be the solution for straightening crooked and crowded teeth or closing gaps and spaces. They are often used to cover discolored or darkly stained teeth.