A computer program is a set of instructions that tells a computer what to do. It is written in a programming language by a programmer and then compiled or interpreted to run on a computer. Programs can perform a wide range of tasks, from simple calculations and data processing to complex operations like artificial intelligence and machine learning. They can be used for various purposes, such as creating applications, controlling hardware devices, or automating tasks. Programs are essential for the functioning of computers and enable users to perform tasks efficiently and effectively.