the.com/box office

means The ticket counter at a theater—and by extension, a measure of how much money a movie, play, or show earns from ticket sales.

from Literally a box: in Elizabethan and later theaters, a 'box' was a small enclosed seating compartment, and the office where you paid to book one became the 'box office.' By the 1700s the phrase had already drifted from the physical booth to mean the takings themselves—how a show was doing financially—which is the sense that stuck when Hollywood took it over in the 20th century.