Mail basically is comprised of three components, the preparation, sending and receiving of mail. Sending mail can be as simple as putting addressed/stamped envelopes in your own mail box for your postman to pick up, to mailing packages or letters at the local post office or using one of the many delivery companies. Receiving mail/packages can also include delivery from your local postman as well as one of the many delivery companies.
Preparing mail/packages to be sent involves labeling with the recipient's name and address as well as the senders. Also making sure packages are sealed and wrapped to postal standards is a good idea. Make sure you are aware of postal laws regarding the types of materials that can be sent in the United States as well as other countries before mailing.
Here are some questions commonly used when discussing the preparation of letters and packages to send.