Think of async/await as syntactic sugar for doing the kind of asynchronous programming when you pass callbacks/continuations and have an explicit event loop. For example, assume that you have an http_request function that looks like this:

    http_request(url, callback)

If you want to make a request, get a value, and then make another request depending on that value, you would need something like:

    def callback(result):
        url2 = get_from_value(result)

        def inner_callback(result):
            print('Final result:', result)

        http_request(url2, print)

    http_request(url1, callback)

This is very complicated, specially because in Python it's not easy to inline callbacks like in JavaScript. And even then, it's sometimes messy and becomes a callback hell.

With async/await you could do something like:

    result1 = await http_request(url1)
    result2 = await http_request(get_from_value(result1))
    print('Final result:', result2)

The await keyword doesn't block like in Perl 6. It suspends the execution and returns the control to the even loop. Then the event loop calls other functions in response to other events. All this happens in a single process and a single thread.

This model is more explicit than the Goroutines of Go or the multiple threads of Perl 6. But it has the advantage that the user has more control over when the execution control flows between different parts of the program. For example, if I have this code:

    await request1()
    # some synchronous code
    await request2()

I am completely sure that nothing will run while the code in the middle of the two request is running. This simplifies a lot of synchronization problems.