Unix & Linux
the posts sure have been slow today..probably cause it's a Sunday. plays Lazy Sunday
back on topic: people have been confused about Unix and Linux for a long time, probably due to the similarities in syntax, usage, and the letters U, N, I and X in both Unix and Linux.
Firstly, Unix is old. It's around 40 years old now, and built at AT&T Bell Labs as a side-project, before AT&T hawked it off to Universities and companies as the OS they should run their mainframes with, and soon, many workstation companies, which also includes Unix experts in their fold, and this is the main reason why many workstations run a Unix-based OS on their machines.
Linux, on the other hand, is pretty young, probably around 18 years old now, and it's not based on Unix, as some people assumed, but rather Andrew Tenenbaum's Minix OS, which he originally wrote as a way to teach his students on Operating Systems design.
Linus soon made Linux Open-Source, and soon many companies and organizations made their own versions of Linux, and that is why we have various types of Linux distributions for us to use, from Ubuntu to Debian to Slackware, etc.
I'm not in the mood to go too technical on the subject, so I would recommend that you check out these links to learn more:
http://wiki.answers.com/Q/What_is_the_difference_between_Linux_and_Unix
http://www.cyberciti.biz/faq/what-is-the-difference-between-linux-and-unix/
One interesting thing tough, both of them started out as side-projects. Dennis Ritchie built it on a spare PDP-7, all because he wanted to play a game that ran too slow on the PDP's native OS, before Ken Thompson and a few other guys noticed it, and tagged along.
Linux was also made as a project by Linus, for no other reason than firstly as a terminal emulator for him to access the Unix servers at his university, before he kept on improving it that it became a complete OS.
https://netfiles.uiuc.edu/rhasan/linux/ - History of Linux
Perhaps an interesting read? Shows relationship of Unix -> Minix -> Linux. And some interesting facts u may or may not care about.