What FaultContract in WCF?

Hi

I am having small clarification in Message and Fault Contract.

fault contract is mainly used to handle the exception that happened in service to the consumer of the service. In other words it is used to customize the message in the service and send it to the consumer.

My doubt is that why should i go for FaultContract. I can use MessageContract or Even i can put some datamember in the datacontract to store the exception and send it to the application.

Hope this is clear. Please let me know if this is not.