An arithmetic logic unit (ALU) is a fundamental component of a computer's central processing unit (CPU). It performs basic arithmetic operations, such as addition and subtraction, as well as logical operations like AND, OR, and NOT. The ALU takes input data, processes it according to specified instructions, and produces output results. The ALU works in conjunction with other components of the CPU, such as the control unit and registers. It is essential for executing calculations and making decisions in computer programs. By handling these operations, the ALU plays a crucial role in the overall performance and functionality of a computer system.