A GPU is a circuit board with a dedicated processor designed specifically to handle intense computational requirements of displaying graphics. These were earlier known as 3D accelerators, because the main job of these units deals with objects represented in 3 dimensions. There are various applications that require a 3D world to be simulated as realistically as possible on a computer screen. These include 3D animations in games, movies and other real world simulations.
It takes a lot of computing power to represent a 3D world due to the great amount of information that must be used to generate a realistic 3D world and the complex mathematical operations that must be used to project this 3D world on to a computer screen. In this situation, the processing time and bandwidth are at a premium due to large amounts of both computation and data.
The functional purpose of a GPU then, is to provide separate dedicated graphic resources, including a graphic processor and memory, to relieve some of the burden off the main system resources, namely the Central Processing Unit, Main Memory, and the System Bus, which would otherwise get saturated with graphical operations and I/O requests. The abstract goal of the GPU, however, is to enable a representation of a 3D world as realistically as possible. So these GPUs are designed to provide additional computational power that is customized specifically to perform these 3D tasks...