Super Delegates are party officials, democrats who are holding higher offices (Senators, members of the house, governors, etc.), and former officers (ex-presidents, vice Presidents, I believe governors, and the like). They are currently, I believe, still leaning a little towards Clinton (not overwhelmingly though), but none are locked into their votes yet. They don't technically vote until the convention, but they endorse early to help their candidate of choice get nominated in primaries. There is a small trend, not a ton, but some, of Clinton super delegates switching over to Obama over the last couple months.