Like SLA, SLS systems can produce complex structures uses laser technology. However, the materials are very different.
Selective Laser Sintering is an additive manufacturing process. The machine builds up layer upon layer of the 3D model, starting with the bottom layer. After some hours have passed, the model is finished.
The material used is a one-part or two-part powder, which can be a metal, plastic, ceramic, or glass. The build tray sits inside a vat of the powder and a laser system aims at specific points on the tray to fuse together the appropriate sections for each layer. The particles are either fully melted or only partially melted to fuse together and to the previous layer. After each layer is finished, the tray drops so that the machine can begin the next layer.
One great benefit of SLS is that is does not require support structures to support overhanging features during printing. This is because the bed of powder supports the model at all times. Most 3D printing processes require some form of support material, which adds to the cost and cleanup time.