This chapter presents NVIDIA general purpose graphical processing unit (GPGPU) architecture, by detailing both hardware and software concepts. The evolution of GPGPUs from the beginning to the most modern GPGPUs is presented in order to illustrate the trends that motivate the changes that occurred during this evolution. This allows us to anticipate future changes as well as to identify the stable features on which programmers can rely. This chapter starts with a brief history of these chips, then details architectural elements such as the GPGPU core structuration, the memory hierarchy and the hardware scheduling. Software concepts are also presented such as thread organization and correct usage of scheduling.