Crystal Skulls and Mayan Legends

What is the legend of the thirteen crystal skulls (featured in the fourth Indiana Jones film)? Are these skulls fake or do they store vast amounts of information (just like computer chips do)?

This video clip, from Top 10 Places of Mystery, explains a bit about them. (Move the cursor forward to :40 to begin the piece on the Mayan legends of crystal skulls.)

Credits

Clip from Top 10 Places of Mystery, from the Travel Channel.