What is an LCG (Living Card Games)?
I believe that Living Card Games is a term used (and owned) by Fantasy Flight Games.

You can read about them on their website.  The basic theory is that they release a core set and potentially endless expansion packs.  However unlike Magic: The Gathering and other collectible card games, each set (core or otherwise) comes complete in each pack.

This should keep the cost much less for LCG's.