3D printing, also known as additive manufacturing, creates three-dimensional objects from a digital file. It works by slicing the digital design into thin layers, then depositing or solidifying material layer by layer to build up the object. This can be done using various methods, like extruding molten plastic, curing liquid resin with light, or fusing powdered material with lasers or binders. Each layer adheres to the previous one, gradually forming the complete object as the process progresses.