The back office of a business is the place where the administrative and operational duties of the business take place, as opposed to the front office where customers are met and served. The term is used with many types of businesses, especially with brokerage firms, according to Investor Words.
Examples of work done in a back office include accounting, personnel, record keeping and compliance. These offices, which are rarely accessible to customers, house support staff and the private offices of administrative personnel. The term originates from the way in which most offices are designed, with the customer-friendly areas in the front and the private spaces in the back, according to Wikipedia.