Postal system

Friendship books (also known as "FBs" in their abbreviated form) are small booklets made by stapling paper together, or are sometimes just sheets or strips of paper.

A letter is a written message from one party to another containing information.

A postmark is a postal marking made on a letter, package, postcard or the like indicating the date and time that the item was delivered into the care of the postal service.

A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage.

An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along with other identifiers such as house or apartment numbers.

Parcel post is a postal service for mail that is too heavy for normal letter post.

Advertising mail, also known as direct mail (by its senders), junk mail (by its recipients), or admail, is the delivery of advertising material to recipients of postal mail.

A post office is a customer service facility forming part of a national postal system.

In philately, indicia are markings on a mail piece (as opposed to an adhesive stamp) showing that postage has been prepaid by the sender.

Pneumatic tubes (or capsule pipelines; also known as Pneumatic Tube Transport or PTT) are systems that propel cylindrical containers through networks of tubes by compressed air or by partial vacuum.

Registered mail is a mail service offered by postal services in many countries, which allows the sender proof of mailing via a mailing receipt and, upon request, electronic verification that an article was delivered or that a delivery attempt was made.

The secrecy of correspondence (German: Briefgeheimnis, French: secret de la correspondance) or literally translated as secrecy of letters, is a fundamental legal principle enshrined in the constitutions of several European countries.

Military mail, as opposed to civilian mail, refers to the postal services provided by armed forces, that allow serving members to send and receive mail.

A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients.

Post riders or postriders describes a horse and rider postal delivery system that existed at various times and various places throughout history.