What the heck is a "superdelegate"?

Question

above says it all

Answer 1

It is the party's way of stealing the nomination for the candidate of their choice, no matter what the voters choice was.

Answer 2

Superdelegates are mostly delegates who are seated automatically based solely on status as a current or prior Party leader or a government official (Bill Clinton is a superdelegate); others are chosen as the primary evolves.

The superdelegates are free to support any candidate.  It's possible for a candidate to win the Democratic nomination for President by receiving a majority of superdelegate votes, regardless of what the popular vote would be.

It's rather complicated, so I've given some links below to help you to understand it better.  

Link 1 -  Overall information re: superdelegates

Link 2 -  Superdelegates Endorsement List

I hope this helps you.  Good luck!