What does 'class prize' exactly mean?

I was notified by the TD that  I was awarded a class prize and left before claiming it.  What exactly is a class prize an how do you earn it?  Thanks for your help, I know this is a very simple question but I'm unclear on it.

The USCF is broken into class divisions. Class A is 1800-1999, Class B is 1600-1799, etc. You won a prize for your rating level in the tournament.

First of all thanks for the reply, I really appreciate it.  But what did I exactly do to win it?  I beat someone that was 200+ points higher rated than me?  I know that the USCF has Classes but what exactly causes you to win the Class Prize and what is the actual definition of Class Prize.  

I'll use your chess.com rating as an example.

Lets say your rating is 1820 and you score 3 points after 5 rounds.

Ok, you didn't win the tournament, but if no one rated 1800-1999 scored better than 3, then you scored the highest in your class.

Almost always it's a cash prize, although sometimes a plaque or something like this.

And when I was doing a little TDing, we'd just mail checks to those who left before collecting money, but if you're in the area that might not be necessary, next time you see the guy be sure to get your money / prize.

Oh, I see, that clears things up.  Thanks so much for the detailed explanation.  Kudos!