What does "APO" stand for?

"APO" is an abbreviation that stands for "Army Post Office." The letters are typically followed by a string of numbers that identify a specific military installation or unit that APO is attached to. An APO associated with a unit is typically mobile and moves as units are deployed.

As of 2014, shipments and mail to an APO must be done through the United States Post Office. In a mailing address, APO takes the place of the city name. Other similar abbreviations include the BPFO, which is short for "British Forces Post Office," and "MPO, which is short for "Military Post Office."