A 3-D printer is a machine that creates three-dimensional objects by layering materials, such as plastic or metal, based on a digital design. It works by following a computer-generated blueprint, which guides the printer in building the object layer by layer, allowing for intricate shapes and details. These printers are used in various fields, including manufacturing, medicine, and art. They enable rapid prototyping, allowing designers to create and test models quickly. Additionally, 3-D printing can reduce waste, as it uses only the material needed for the object, making it an efficient production method.