From The Art and Popular Culture Encyclopedia
Mail, or post, is a method for transmitting information and tangible objects, wherein written documents, typically enclosed in envelopes and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.
In principle, a postal service can be private or public. Governments often place restrictions on private postal delivery systems. Since the mid-19th century national postal systems have generally been established as government monopolies with a fee on the article prepaid. Proof of payment is often in the form of adhesive postage stamps, but postage meters are also used for bulk mailing.
Postal systems often have functions other than sending letters. In some countries, a Postal Telegraph and Telephone (PTT) service oversees the postal system as well as having authority over telephone and telegraph systems. Some countries' postal systems allow for savings accounts and handle applications for passports.