Quite a few technologies are capable to do 3D printing. The main differences are how layers are built to create parts.
SLS (selective laser sintering), FDM (fused deposition modeling) & SLA (stereolithograhpy) are the most widely used technologies for 3D printing. Selective laser sintering (SLS) and fused deposition modeling (FDM) use melting or softening material to produce the layers.
YouTube has many videos on the different printing processes with examples. Generally, the main considerations are speed, cost of the printed prototype, cost of the 3D printer, choice and cost of materials and color capabilities.