When it comes to 3D printers, there’s a bunch of different technologies. Here is one called a DLP (digital light projector) SLA (stereolithography apparatus). Basically it works like a normal SLA, except the way it handles the file. Rather than slicing the 3D file into tool paths, the file is split into different images that get projected layer by layer. Here is a better description from the person who DIY’d the 3D printer shown here.