Claims based authentication is not a new concept , but it was recently adopted by Microsoft and other major software giants as a standard.
The main purpose and use of the CBA , is authentication against cloud services and also to be used with Federated Identity services.
Some core concepts include
STS : Security Token Service .
RP : Relying Party
- Also read more on the WIF ( Windows Identy Foundation ) that is part of .NET 3.5 and 4.0
- Also read more on the Geneva Project ( later changed to ADFS 2.0 ) Active Directory Federation Services , if you plan to use your own AD as an account /Identity silo .
That would open up a whole world of
 How can I Use my Cloud application , yet use my local AD to do authetication.
 how can I extend my application to use open Identiy providers like ( Google ID , Live ID , Amazon ws , Yahoo ID etc. )
I was concerned about how to make this work with the new SharePoint 2010 directly , I noticed that out of the box , no Identiy Provider list to choose from (silly me). from which I started finding out more about this whole project.
I came across this blog during my researh and I believe it is the most detailed.
It is by Steve Peschka, (great job Steve)
Hope that puts you on the right track.
Best of Luck