what is a relay in a pileup?
 

Newbie question: This morning on 20m I was listening to a pileup for a
mobile in Minnesota who was 33 from my G5RV near Seattle. I could
hear some of the callers but not many. Suddenly a very strong signal
came on offering to relay for the mobile (I think). It was very rapid
fire for quite a while, and then the strong signal bowed out and
someone thanked him for the help.

It was all happening to fast for me to follow. What was I hearing?

KD7VEY