SLA creates objects by using an ultraviolet laser beam to selectively cure a  polymer resin layer by layer. The materials, which are photosensitive  thermoset polymers; come in a liquid form. SLA belongs to the group of  additive manufacturing technologies, also known as vat photopolymerization.  SLA is generally the best 3D printing technology that is typically used for  surfaces needing a smooth finish.

SLA is extremely accurate. Its parts have the highest resolution and finest  feature detail. SLA is very popular due to its versatility. Due to recent  improvements in print speed and materials, it can be used for virtually  anything, competing with engineering thermoplastics in mechanical properties  and injection molding in finish and detail. 

Another huge advantage of SLA is printing parts within 24 hours. Where many  production technologies have multi-day print cycles, being able to start a  machine and a few hours later have printed parts is a huge advantage of this  technology when quick turn parts is a necessity.

Source:https://www.rapidmade.com/rapidmade-blog/2021/3/12/an-introduction-to-sla-3d-printing

Features:

·Accurate

·High resolution

·Fine detailed feature

·Versatile

Selective Laser Sintering (also called as SLS) is another powerful 3D printing  technology. It uses a high-power laser to fuse small particles of polymer  powder into a solid structure based on a three-dimensional model. The laser  selectively fuses powdered material by scanning cross-sections generated from  a 3-D digital description of the part (for example from a CAD file) on the  surface of a powder bed. After each cross-section is scanned, the powder bed  is lowered by one layer thickness, a new layer of material is applied on top,  and the selective laser sintering process is repeated until the part is  completed.

SLS technology is widely used in many industries as its ability to easily make  complicate 3D profile. The advantages are good chemical resistance, wide  variety of materials with characteristics of strength, durability and  functionality. The parts are often used as substitute injection molding parts  because of its reliable mechanical properties.