Electronic mail (e-mail) is a method of sending and receiving messages between computers over ordinary telephone lines. The file is converted by a modem to an appropriate signal and transmitted at a specific rate (baud). To use e-mail, one requires a computer, a modem, a connection to an external phone line, communications software, and a subscription to a bulletin board or other electronic service. Mastering all of the required technologies is complex. Though books are available, most people learn the process from friends. This "networking" is encouraged by the very nature of the electronic community.
The actual structure of e-mail messaging is similar to hypertext. Generally, one leaves a message for a particular person, or for all participants in a given area. These meeting sites on a given topic are often termed "conferences." Specific ongoing conversations are known as "threads." A thread is born when there are enough messages on a particular topic for the conference mediator (or other participant) to justify its existence. As interest grows, participants comment on each other's messages, adding examples, counter-arguments, claims, and so on. The message tree branches and eventually either dies out due to lack of interest, or spawns further threads.
When posting an e-mail message, one usually includes in the header the name of the thread or recipient. This creates a link to previous messages/nodes. Thus the on-line hypertext is a multi-author web of conversation.