The graphics processing unit (GPU) became an undoubtedly important computing engine for high-performance computing. With massive parallelism and easy programmability, GPU has been quickly adopted by various emerging computing domains including gaming, artificial intelligence, security, virtual reality, and so on. With its huge success in the market, GPU execution and its architecture became one of the essential topics in parallel computing today. The goal of this chapter is to provide readers with a basic understanding of GPU architecture and its programming model. This chapter explores the historical background of current GPU architecture, basics of various programming interfaces, core architecture components such as shader pipeline, schedulers and memories that support SIMT execution, various types of GPU device memories and their performance characteristics, and some examples of optimal data mapping to memories. Several recent studies are also discussed that helped advance the GPU architecture from the perspectives of performance, energy efficiency, and reliability.