Which jobs are front of house?
Servers, bartenders, hosts, ushers, registration staff, coat check and guest services. If your job is to face guests, you're front of house.
Front of house vs back of house
Back of house is everything guests don't see: the kitchen, dish area, storage and loading dock. At most catered events the two sides meet at the pass, where servers pick up plates from the kitchen.
What FOH means in live sound
At concerts and conferences, FOH also means the front-of-house sound position: the mixing desk out in the audience where the sound engineer works. When a production crew says to meet at FOH, they mean the desk.