I have been struggling with why LINQ (Language Integrated Query) was even useful for the last few weeks, and then finally the penny dropped. While I could go into an elaborate explanation of it inner wonders, I would prefer to share with you the source of my epiphany. I stumbled across a great video from Charlie Calvert that includes a interview with Anders Hejlsberg (Chief architect of C#).
At first I was looking into LINQ as a replacement for direct SQL query access, or just another way to write or access XML, however, LINQ is much more. It is a common way to link (pardon the pun) all of the above and more. I was able to really grok the concept as I listened to Anders speak. It really figures to join our various data sources and the programming world in a very intuitive way. It has a very specific nomenclature to describe data relationships much the same way SQL does (select, where, group by, etc).