Front of house includes all of the customer touch points in a restauant. It's where your customers order and dine. It includes everything from the host stand and waiting area to the dining room, bar, outdoor seating, and restrooms.
The back of house, meaning all the behind-the-scenes action that customers typically do not see, is also referred to as BOH. This is usually primarily the kitchen, where the food is prepped and cooked. It can also include employee break rooms and any office space and storage.
