Joomla related terms:
A variant of the Unix Operating System written by some bloke named Linus. The name Linux is a weird mix of Linus and Unix.
Long story short - some college kid does a project - he builds the inner workings of an operating system. When he is finished he could sell it or develop it commercially. He picks a third way - he releases it to the world any one can develop it, but it must be passed on likewise - anyone can have what you do with it. Whilst not the first 'Open Source' software project he popularises the movement bringing it to 'mainstream' (well mainstream geek) awareness.