Explain what the term 'escaping closure' means in the context of programming.

In programming, especially in Swift for iOS, the term "escaping closure" refers to a closure that can be called after the function accepting it has already finished executing.

By default, closures in Swift are considered "non-escaping" — they must be called within the body of the function. If a closure is stored for later use (for example, asynchronously), it needs to be marked as @escaping.

Example:

func performAsyncTask(completion: @escaping () -> Void) {
    DispatchQueue.global().async {
        // some work
        completion() // called later, after the function exits
    }
}

Here, completion is an escaping closure because it is called asynchronously after performAsyncTask has finished.