To annoy, obfuscate and confuse in about equal measure.
Or, if you prefer, it's a technology for allowing us to distribute processing to remote sites and to transfer data between them.
You really need to start with google:
https://www.google.co.uk/search?q=WCF&aq=f&oq=WCF&aqs=chrome.0.57&sourceid=chrome&ie=UTF-8[
^] and follow a few of the top links.
In future, please try to do at least basic research yourself, instead of wasting your time and ours.