Unix is a product of AT&T Bell Labs, currently owned by The Open Group.
Linux, a term trademarked by it's original author Linus Torvalds, is a UNIX-like kernel intended to be fast, stable, and
free.
There's no shortage of
information on the web about Linux. You can download a
bootable cd and get started playing around without installing anything.
Other options include
Cygwin, a windows port of many Unix tools, and
vmware, which allows you to run other OS's without leaving your familiar Windows desktop (VMWare Player is a $0 product).