An algorithm is a set of instructions for solving a problem or completing a task. Algorithms are often used to perform calculations, data processing, and automated reasoning tasks. They can be implemented in software, hardware, or a combination of both. Algorithms are an essential part of computer science and are used in many different fields, including machine learning, data analysis, and computer graphics. Some common characteristics of algorithms include input, output, and a set of well-defined steps for achieving the desired result.