Other forms: box offices
A box office is the area of a theater or other venue where you can purchase tickets. If you buy your tickets online, they can usually be picked up at the box office.
As well as the physical place where tickets are sold, box office is used to describe all the money a movie or play makes from ticket sales. If a film is described as "a disappointment at the box office," that means that the producers hoped to sell more tickets than they did. Box office has been used since the 18th century, possibly deriving from the offices where tickets were sold for private theater "box seats."