Post Office Protocol. A standard for people to download their e-mail to their own computer. A POP (or POP3) server holds peoples e-mail until they download it to their personal computer.

Send Mail Transfer Protocol. The method used to send mail on the internet. Most commonly used to refer to an SMTP server, which is used by e-mail programs to send mail out on the Internet

When you send mail to an address that is forewarding, the e-mail will get sent to wherever the forewarding account is set up to send it.

An exploder is much forewarding, but with more than on recipient. Whenever e-mail is sent to the exploder address, it is forwarded to every e-mail address in the exploders list.

An autoresponder will automatically respond to the sender with a precomposed message, as well as sending the original message to a specified address.

  Other terms

A virtual web server is used to refer to a web server that actually holding many other website (and is the web server for those sites). The server is "virtual" because it is not a dedicated webserver, but is sharing resources with other "virtual" web servers. In fact, most web sites these days are on virtual web servers, only larger companies can afford a dedicated webserver.