Go to
www.windowslive.com to find out more about Windows Live. Lots of good content there and all of it written by people use who the products, not by Microsoft.
Here's my short answer:
Mesh is a synchronisation platform on which developers can build applications. Windows Live is a set of tools and services for email, photo sharing, blogging, instant messaging and social networking. The main thing they share in common is the Windows Live ID login which is the same login you used to post your question above.
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