An asynchronous function is a type of function in programming that allows tasks to run independently without blocking the main thread. This means that while one task is waiting for a response, such as fetching data from a server, other tasks can continue executing. This is particularly useful in web development, where it helps maintain a smooth user experience. In many programming languages, such as JavaScript, asynchronous functions are defined using the `async` keyword. They often work with Promises, which represent a value that may be available now, or in the future, or never. This approach enables developers to write cleaner and more efficient code.