What is a coroutine?

Question

What is a coroutine? How are they related to concurrency?

Answer 1

Coroutine is similar to subroutine/threads. The difference is once a caller invoked a subroutine/threads, it will never return back to the caller function. But a coroutine can return back to the caller after executing a few piece of code allowing the caller to execute some of its own code and get back to the coroutine point where it stopped execution and continue from there. ie. A coroutine has more than one entry and exit points