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Callbacks are a fundamental concept in computer programming, particularly in asynchronous operations. A callback is essentially a function that is passed as an argument to another function. This other function will then "call back" the passed-in function at a later time, typically when a certain operation has completed or an event has occurred.

This pattern is widely used to handle events and manage operations that take time to complete without blocking the main execution thread. For instance, when fetching data from a server, a request is initiated, and instead of waiting idly for the data to arrive, the program can continue with other tasks. Once the data is received, the pre-defined callback function is executed, processing the retrieved information.

The primary benefit of using callbacks is enabling non-blocking I/O and event-driven programming. This leads to more responsive applications, especially in environments like web browsers or server-side applications that handle numerous concurrent requests. Callbacks help manage complexity in asynchronous workflows, allowing developers to define what should happen after an operation finishes. While effective, deeply nested callbacks can sometimes lead to what is known as "callback hell," a situation where code becomes difficult to read and maintain due to excessive indentation. Modern programming languages and libraries often offer alternative patterns like Promises or async/await to mitigate this issue.