This site looks like it has the answers you need. I also added another explanation.What's the difference between porcelain veneers and dental ...
www.animated-teeth.com/...dentistry/t_porcelain_veneers_crowns.htm
A crown encases the entire tooth, a veneer just its front side. A fundamental difference between veneers and crowns is how much of the tooth they cover over. Crowns typically encase the entire tooth, whereas veneers only cover over its front surface (the side that shows when the person smiles).