The term "Linux" refers to a group of operating systems based on UNIX. There are many different distributions, and they all differ from one another significantly. If you have no experience using *nix operating systems, it may just be easier for you to purchase a copy of Windows and install it on the laptop. If you want to learn a bit about Linux, but would still like the familiarity of Windows, you can install both on the laptop, and experiment with your Linux installation as a learning endeavor.
Depending on the distribution of Linux, it may come with a GUI or it may not. If you have never used a *nix operating system before, you will probably want to start out with some graphical user interface. If you are comfortable with the commandline, though (maybe you are a DOS user?) you may feel right at home under a commandline *nix environment.
Linux is certainly not "rubbish" though. UNIX is every bit as powerful, and arguably, more versatile than any other operating system in existence. It is used by professionals and home users alike across the world, and is the main operating system used for servers of all types. Asking about the differences though, is kind of like asking the difference between apples and oranges...or OS X and Vista. It's hard to know where to begin. Perhaps the first thing you will notice about *nix is the directory structure. This is pretty much uniform throughout distributions. if you are used to Windows, you may also be struck by how the line between "location" and "filename" is blurred. You could say that filename==location. This can be a difficult concept at first, but you will grow used to it soon.
Of course, under *nix, you will not have to worry about viruses. Plus, you can brag to your friends that you use Linux as your primary operating system - that's always nice.