UNIX and LINUX, whats the diff?
Haha, not a lot, and quite a bit (depending on who you ask).
Unix is/was a proprietary operating system developed at AT&T. It was licensed to businesses, governments and universities for use. While it was open to use, it was not available to individuals, and the fees to use it were pretty steep.
Around 1983, Richard Stallman was working on an operating system named GNU [Gnu's Not Unix] that would be "Unix-like", and be able to perform the same functions as a Unix system. Around 1991, Linus Torvalds wrote a kernel he named Linux, which would later be put with the GNU operating system. The combination today is what many call a Linux operating system (or GNU/Linux, more appropriately).
Unlike Linux, FreeBSD is an actual continuation of the Unix code that was used at Berkley University; while GNU does not contain any Unix code.
However, a lot of the programs FreeBSD uses are from GNU (such as gcc), and this reduces the difference between the two in some people's eyes. Since FreeBSD is open source, as well as with a more liberal (irony) license, code can be taken under the BSD license and used under the GNU license, as well. However, GNU software can not be relicensed under the BSD license; so it's a one way street.
Mainly, it comes down to ideals.