What is a "X" flood zone and a "shaded-X" flood zone?

With the new set of maps, FEMA has changed the names of a couple of flood zones. The old "C" zones are now called "X" and the old "B" zones are now "shaded-X". There is absolutely no difference in the meaning, just the name changed. Neither of these zones are considered high risk, and neither zone requires the purchase of federal flood insurance.