Hunter is a term that refers to an individual MouseHunt player. Every player who adds the MouseHunt application gains this title. There are several ranks of hunters, which affect how and where one can hunt.
Every hunter can have several people in their hunting group. Your hunting group grows if you have more Facebook friends online and hunting in your location. With a larger hunting group, your friends can sound the horn for you, sending you on more hunts, so long as you are online within the last hour. Otherwise, only the trap checks can happen without the hunter's input. You must log into MH once per 24 hours to receive the trap checks which happen on the hour for 24 hours. (12:00, 1:00, 2:00...)