What is e-mail?

E-mail (electronic mail) is, on the one hand, a system for the computer-based management of letter-like messages and their transmission via computer networks, especially the Internet. On the other hand, the messages themselves transmitted in this electronic way are also referred to as e-mails.

Along with the World Wide Web, e-mail is an important Internet service, not least because e-mail makes it possible to send text messages as well as digital documents (i.e., graphics or Office documents, for example) around the world typically in a matter of seconds.

Unlike telephone or chat, which enable simultaneous (synchronous) communication, e-mail - like letter post - is an asynchronous communication medium: the sender sends his message regardless of whether the recipient can receive it immediately or not.

See also:
Wikipedia: E-Mail