Traditional 3D printers work by building up material, layer upon layer. The technical term for this is Computer Numerically Controlled (CNC) Additive Fabrication. But that’s a mouthful, so people just call it 3D printing.
The Glowforge takes a different approach. It is subtractive instead of additive: you put a piece of material like leather, wood, or acrylic in the machine and it carves out your product using laser energy. The proper name for the tool is a CNC laser cutter engraver, but that’s a mouthful, so we call it a 3D laser printer.