In response to the complexity of Threading in .Net, async and await keywords step in .Net 4.5 to make asynchronous programming easier. Asynchrony is quite essential when doing certain tasks like: calling web services, working with files and working with images. Microsoft technologies like Windows 8 and Windows Phone rely heavily on this new async programming.
So here is an elementary sample on async and await:
Async and await are always a pair. You can have multiple awaits in one method as long as it is marked async.
For more visit full msdn documentation.