"WCF" stands for Windows Communication Framework. WCF is the replacement for WSE (now obsolete), ASMX (the old ASP.NET Web Services), and to some extent, is also a replacement for .NET Remoting.
WCF covers all of the web services scenarios covered by ASMX and WSE, and then adds support for many more, including binary communication over TCP/IP, communication over message queues and named pipes, and many more.
A rich extensibility model permits both Microsoft, third party developers, and you, to extend WCF for future requirements. See the Cloud Computing article, and the Foundations: Working with the Service Bus articles in the April 2009 issue of MSDN Magazine to see how WCF has been extended to some very modern scenarios.
All new web services development should be in WCF, if at all possible.
