A computer operating system developed by AT&T Bell Labs and used by many people at the same time (it is multi-user) and has TCP/IP built-in. It is the most common operating system for servers on the Internet.

An acronym for "Uniform Resource Locator" this is the address of a resource on the Internet. Such as a html file http://www.redpebble.ie/ brings you to the RedPebble home page. The resource can be an HTML page like the one you're reading now, an image file, a program such as a common gateway interface application or Java applet, or any other file supported by HTTP.