what is the use of wcf?

Let's take a simple example. You need some mobile carrier to talk to someone. for e.g. airtel, vodafone, idea etc. 

Now these dayz you need to have internet, Value added services etc. and the same mobile carrier is being used for those purpose. 

Think if Mobile carrier is WCF and your basic need of communications are of Internet, Intranet or Interprocess. Single WCF will provide you flexibility to create communications based on your needs. 

Hope this make sense.

http://en.wikipedia.org/wiki/Windows_Communication_Foundation

http://msdn.microsoft.com/en-us/library/ms731082.aspx