From StrategyWiki, the free strategy guide and walkthrough wiki

The Quake Engine is the 3D engine created by Id Software for use in Quake. It is considered an intermediary engine between Id Tech 1 and Id Tech 2 (the latter is also known as the Quake II engine). This was one of the first popular 3D game engines, and one of the first to utilize an OpenGL engine to take advantage of 3D graphics cards.