CPU stands for "Central Processing Unit" and is the main processing unit of a computer. It is responsible for executing commands and processing data. The CPU is the "brain" of the computer and performs all the basic calculations and tasks.
GPU stands for "Graphics Processing Unit" and is a specialized processor unit that specializes in processing graphics and image information. It is mainly used for rendering 3D graphics, video playback and other computationally intensive graphics applications. The GPU is especially important for gaming computers and other tasks that require high graphical performance.