Async and Await

public async Task MyMethodAsync()
{
    Task<int> longRunningTask = LongRunningOperationAsync();
    // independent work which doesn't need the result of LongRunningOperationAsync can be done here

    //and now we call await on the task 
    int result = await longRunningTask;
    //use the result 
    Console.WriteLine(result);
}

public async Task<int> LongRunningOperationAsync() // assume we return an int from this long running operation 
{
    await Task.Delay(1000); //1 seconds delay
    return 1;
}

Ok, so what happens here:

1. Task<int> longRunningTask = LongRunningOperationAsync(); starts executing LongRunningOperation
2. independent work is done on let's assume the Main Thread (Thread ID = 1) then await longRunningOperation is reached.

Now, if the longRunningOperation hasn't finished and it is still running, MyMethod() will return to its calling method, thus the main thread doesn't get blocked. When the longRunningOperation is done then a thread from the ThreadPool (can be any thread) will return to MyMethod() in its previous context and continue execution (in this case printing the result to the console).
A second case would be that the longRunningOperation has already finished its execution and the result is available. When reaching the await longRunningOperationwe already have the result so the code will continue executing on the very same thread. (in this case printing result to console). Of course this is not the case for the above example, where there's a Task.Delay(1000) involved