A compiler is a special program that translates code written in a high-level programming language, like Python or Java, into machine code that a computer's processor can understand. This process allows developers to write code in a more human-readable format while ensuring that the computer can execute the instructions efficiently. Compilers perform several tasks, including lexical analysis, syntax analysis, and code optimization. During lexical analysis, the compiler breaks the code into tokens, while syntax analysis checks for grammatical correctness. Finally, code optimization improves the performance of the generated machine code, making programs run faster and use fewer resources.