That is where one Ham operator (fox) goes to a fixed location and starts broadcasting, for our beginners group he was just talking on a specified frequency. I was teamed up with a more experienced Ham who had done this before, we were one of five teams of hounds. We used directional antennas to attempt to triangulate the direction the signal was coming from.
Here is a picture of one of the antenna's used by one of the Ham's:
We would take a bearing and draw a line on a city map we had. We would then drive to a different location and get another bearing on the signal from the fox's radio signal. My partner and I took readings from 5 different locations around the city. We had four block area, but the fox started having radio problems, so the hunt was called off early. We had been driving around getting readings for just under two hours and the hunt was supposed to go for two and a half hours. We met back at starting gathering point and compared notes. It turns out the none of the teams had come anywhere close to locating the fox.
Here are some links to some information on Ham Radio Fox Hunts.
https://www.qrpfoxhunt.org/
https://www.n4nrv.org/fox-transmitter-hunting/
http://www.homingin.com/equipment.html