3D printing is an additive manufacturing process that creates a solid object by building it up layer by layer. It allows for complex designs and reduces waste compared to traditional subtractive manufacturing. Common 3D printing techniques include selective laser sintering (SLS) which uses a laser to fuse powder materials, stereolithography which uses a UV laser to cure liquid resin into layers, and fused deposition modeling (FDM) which extrudes melted thermoplastics to build the object layer by layer. 3D printing has applications in prototyping, modeling, and producing custom parts and its use may expand to allow distributed on-demand manufacturing.