SLA (Stereolithography) and DLP (Direct Light Processing are similar technologies. They both use a photopolymer resin that is solidified by a certain wavelength of UV light. 

For SLA a small laser traces out the shape of each layer. For DLP a projector projects the whole layer at the same time to solidify the resin. Since both are done with light this gets much finer detail, much higher resolutions and an overall nicer looking print.

Although more expensive than FDM, SLA and DLP give you an almost completely finished product.