P.O. Item is a term used to describe items that are sent through the mail. The acronym stands for four different types of mail: ENV (envelope), LTR (letter), PCL (parcel), and STP (stamp). Each of these items can be sent through the postal service, and each has its own unique characteristics. Envelopes are typically used to send documents or other items that need to be protected from the elements. Letters are usually used to send written correspondence, such as letters or cards. Parcels are larger items that require more protection, such as packages or boxes. Stamps are used to pay for the cost of mailing items.