A coroutine is a special type of function that allows for cooperative multitasking in programming. Unlike regular functions that run from start to finish, coroutines can pause their execution and yield control back to the caller, allowing other tasks to run. This makes them useful for managing asynchronous operations, such as handling multiple tasks without blocking the main program flow. Coroutines are commonly used in languages like Python and JavaScript to simplify code that deals with events or I/O operations. They help improve performance and responsiveness by enabling developers to write code that appears sequential while actually running multiple tasks concurrently.