Stereolithography (SLA) is a form of 3D Printing technology that uses a photoreactive resin to create models layer by layer using a process by which light hardens the resin to form an object.
Selective laser sintering (SLS) is similar to the SLA process except that it uses a laser to sinter powdered material aiming the laser at points in space defined by a 3D Model, binding the material together to create a solid structure.
Fused Deposition Modeling(FDM) or Fused Filament Fabrication(FFF). The most common method of 3D printing, a process whereby a filament of material is deposited or extruded layer by layer vertically to form a 3D model.