My youngest son got me hooked on the Marvel movies. Just put it in my Netflix saved DVD queue.
Most of the Marvel Studios movies have included what will eventually be known as the Infinity Stones.
Here is a nice summary of where they are and clues to what they do:
http://www.ign.com/wikis/marvel-studios-cinematic-universe/Infinity_Stones
It will all come to a head with Avengers Infinity War and Avengers 4 which, last I knew was still untitled. The movies are being shot back-to-back.