What is a callback function?

A callback function is defined as a function that is passed as an argument to another function. This allows it to be invoked at a later time, typically after the completion of a specific task or event. This mechanism is particularly useful in asynchronous programming, where a function needs to execute certain code after a task is completed, such as an API call or a timer event.

Callback functions help maintain the flow of control in programming, allowing developers to specify custom behavior at precise stages in the execution of another function. By passing a callback function, you can ensure that specific actions occur only after certain conditions are met or events are completed.

In contrast, the other choices do not accurately reflect the definition of a callback function. While a function designed for error handling could use the concept of callbacks, it does not encompass the broader purpose of callbacks in programming. Similarly, the notions of functions that cannot be reused or are compiled at runtime do not pertain to the concept of a callback. The essence of a callback is its role in enabling more flexible, asynchronous, and modular coding practices.