A post office is a local branch of the United States Postal Service, where mail is received and dispatched to individuals and businesses in a given community. A post office usually has postal clerks who receive and process mail, and it's also the place from which mail carriers pick up mail they deliver on their local routes. The office handles USPS business, including mail and package sorting, delivery and forwarding, sales of stamps and other postal supplies, change-of-address requests, and other administrative functions.
In some small communities, the local post office may be located within a commercial business. In communities both large and small, a post office may serve as a local passport office at which passport applications are received and undergo initial processing.