Unix was intended for the workplace and all by itself is nothing more than a black screen that you type code into, usually BASH.
A few years back an enterprising young college fellow came up with the bright idea to write a piece of code for Unix, make it part of the piece of the puzzle and Linux was born.
Linus Torvalds is the fellows name and he's still writing and improving the kernel today.
Take the LI from Linus, drop the U in Unix and combine them and you have Linux.
Linux is Unix, it just has a kernel to allow us to be able to have desktops, sound, pictures and nearly everything else a windows user would see, hear and do.
What is referred to as Unix today in my opinion still could be called Linux because it has a graphic display and almost everything else like Linux.
It has a kernel, just not one written by Linus.
It's Called the BSD's for Berkley Systems Database.
DesktopBSD would have to be my favorite.
They're more Unix than Linux even though you can't see any difference with your naked eye.
Their philosophy and way of doing things are different thus lending a bit more to the bend in the learning curve and making the distributions more for a business atmosphere rather than a home desktop, even though for a lot of people it's the perfect home desktop, it just depends on what you want to use it for.
The BSD's or Unix operating systems are stable but tend to run a little behind the times which works for a lot of people as it just lends more to the stability.
They don't run flash very well as of yet and most of us use flash to see all the pretty moving colored pictures in websites among other things.
A BSD user will more than likely use his system for work and the rock solid stability that's needed, not play.
Linux is more versatile [IMO] and very, very close to the stability of BSD/Unix, more adaptable for work or play, more likely to be cutting edge, able to utilize java runtime, flash as well as all needed codecs.
Cutting edge can be a good thing and a bad thing, it all depends on the mindset of the distribution creator, the users and developers.
There are a lot of distributions that are cutting edge and some have always served me fairly well stability wise.
Some distributions are so simple to install a ten year old could do it, some are so complicated I've never been able to install them and I'm almost a veteren 'nix user myself.
There are even bleeding edge distributions and they usually don't lie about it on their home page hype.
Since you asked the question you're obviously new to the 'nix world.
I'd steer clear of the BSD's for now and find yourself a Linux distribution that might interest you, just don't pick a bleeding edge one. They're very time consuming and frustrating to keep usable.
In fact, if you want a list of all the available 'nix distro's out there, just google distrowatch.
If you want, I'll recommend a few.
Just remember though, Linux isn't Windows and was never meant to be, so don't make a switch thinking it's all peaches and cream and everything nice, there's a learning curve to everything that's new.
There can be good things and bad things involved in making a switch.
Linux can make an old 20 gigabyte hard drive, 256 megabyte ram, pentium 3 processor computer scream with speed and dependability and out perform a brand spanking new pc with Vista on it.
I do it daily.
On the flip side if you take a brand spanking new dual core processor it can make you weep in frustration trying to make Linux run on it.
The reason is, Linux was geared, developed and written after Microsoft was and was geared for the computers of the pentium 3 processor era, not to say it doesn't function fine on up to date hardware, it does, it just takes a bit of tweaking and it also depends on how cutting edge the distro is.
Linux does have a problem with printers/scanners so I'd advise checking out any distro's hardware list.
Hewlett Packard is the friendliest.
The same goes for graphics cards.
I'd advise knowing what card you have there as well.
Nvidia and ATI cards are the best to have and use.