Front of House refers to both the mixing position and the sound system facing the audience. The FOH engineer controls the main speakers — what the crowd hears — from a mixing console typically positioned in the middle of the venue.
The FOH engineer's job is to balance all inputs (vocals, instruments, playback) into a clear, powerful mix that fills the venue evenly. This requires adapting to the room's acoustics, managing feedback, and responding to the performance in real time.
FOH is separate from monitor mixing, which handles what the performers hear on stage through wedges or in-ear monitors.