A Fibers (or coroutine as called in other languages) are special functions that can be interrupted at any time by the user. When a conventional function is invoked, execution begins at the start, and once a function exits, it is finished. By contrast, Fibers can exit by calling other Fibers, which may later return to the point where they were invoked in the original coroutine:

	func main() {
		var fiber = Fiber.create({
			System.print("fiber 1");
			System.print("fiber 2");
		System.print("main 1");
		System.print("main 2");
		System.print("main 3");
	// Output:
	// main 1
	// fiber 1
	// main 2
	// fiber 2
	// main 3

TO DO: more explanations and examples