Quad Swiss

A quad is a four player round robin.

If there are twelve people in a tournament, to play in a quad format, you take the 12 players, and put them in order of their ratings.  Then, the top 4 play a round robin against each other, the next four play a round robin against each other, and the four lowest play a round robin against each other.  Each round robin requires three rounds of play, for a total of six games.

If there are 14 people, then the top four play each other, the next four play each other, and the bottom 6 play a three round mini-swiss. (Just a Swiss, really, but called "min" because of the small numbers.)  Some directors would have the top six play a three round miniswiss. 

...

The quad format does not produce an overall winner.  It only produces a winner within each quad.  It's a good format for a schedule with time available for only three rounds, and low prizes.  Every player gets to play three rounds of Chess against players that are roughly equal in rank, and usually has at least a passing shot at first place within his group.

I'm new to this.  What is a Quad Swiss tournament versus just a Swiss Tournament?

You have to subscribe to the tournament (Play / Live Chess / Tournament / Choose one / Subscribe) and be ready when it starts.

Yesterday I subscribed to a 30/0 Swiss Quad and 5 Minutes after the start I resigned (I think there was an odd number and I had to wait for the second round). 

Choose a (already started) Arena Tournament and you can just play.

Long answer: https://support.chess.com/customer/en/portal/articles/1444927-how-do-live-tournaments-work-where-can-i-join-one-?b_id=12321