Linux
 

What the hell is a Linux?

Well, Linux isn't an operating system (Windows, MacOS) like most people believe, linux is just the core or engine which is called "kernel", for example if you have a car, Linux is the engine, and the car is the complete operating system, so the engine is useless without the other parts, and the other parts are useless without the engine, the other parts being the programs like Office, Corel, among others.

So a full operating system using linux could be Debian, Mandriva, SUSE, Fedora, etc, etc.

Hope that this gives you the general idea

Aside from the fact that given the description of this particular forum this is clearly way off topic, this is also clearly flamebait, but I'll answer it anyway. Read this and most of this.

something that you run on a computer that lets you run other software.

titanium_geek