Assembly language is a low-level programming language that is closely related to machine code, which is the set of instructions executed directly by a computer's CPU. It uses symbolic representations of binary instructions, making it easier for programmers to write and understand than raw machine code. Each assembly language is specific to a particular computer architecture, meaning that code written for one type of CPU may not work on another. Assembly language allows programmers to perform tasks with fine control over hardware, such as managing memory and optimizing performance. It is often used in systems programming, embedded systems, and situations where direct hardware manipulation is necessary. While it requires a deeper understanding of computer architecture, it can lead to highly efficient code.