This chapter defines some basic terminology and provides some historical background, as well as information sources related to computer graphics. Graphics can be two- or three-dimensional; images can be completely synthetic or can be produced by manipulating photographs. A key part of using graphics libraries is dealing with a graphics application program interface (API). An API is a standard collection of functions to perform a set of related operations, and a graphics API is a set of functions that perform basic operations such as drawing images and 3D surfaces into windows on the screen. Every graphics program needs to be able to use two related APIs: a graphics API for visual output and a user-interface API to get input from the user. Many graphics programs are really just 3D numerical codes. Numerical issues are often crucial in such programs. In graphics programs, there is an alternative to traditional debugging that is often very useful.