What is Projection?

Projection, in a general sense, refers to the technique of displaying or presenting information (images, data, etc.) onto a surface. Common uses include: projecting images from projectors onto screens, displaying heads-up displays (HUDs) on windshields, and creating augmented reality experiences by overlaying digital information onto the real world. In mathematics, projection is a mapping of a set (or other structure) into a subset of itself (or onto another such structure), and is a generalization of the idea of casting a shadow onto a plane, for example orthogonal projection (e.g., a shadow) and perspective projection (e.g., a photograph).