what is WCF and how we can use in ASP.NET??

Windows Communication Foundation (WCF) is a framework for building service-oriented applications. Using WCF, you can send data as asynchronous messages from one service endpoint to another. A service endpoint can be part of a continuously available service hosted by IIS, or it can be a service hosted in an application. An endpoint can be a client of a service that requests data from a service endpoint. The messages can be as simple as a single character or word sent as XML, or as complex as a stream of binary data. A few sample scenarios include:

• A secure service to process business transactions.
  
  
• A service that supplies current data to others, such as a traffic report or other monitoring service.
  
  
• A chat service that allows two people to communicate or exchange data in real time.
  
  
• A dashboard application that polls one or more services for data and presents it in a logical presentation.
  
  
• Exposing a workflow implemented using Windows Workflow Foundation as a WCF service.
  
  
• A Silverlight application to poll a service for the latest data feeds.