foh engineer is the person at concerts who you see operating the mixing console. foh stands for "front of house"
this person is highly under appreciated. when the show sounds great, everyone praises the band, when the show sounds bad, everyone blames the engineer.
person one: wow that show sounded great!
person two: yeah, lets applaud the band, but did you hear the opening act? they sucked!
person one: oh, no they are good, it was just the foh engineers fault.