Linux is a freeware Operating System (OS) that you can download on their site. A lot of people like it because it's free, and like that other guy said, a lot of hacking programs work with Linux. For example, Aircrack -ng is a wi-fi password cracking tool, and although there is a Windows version, the Linux version is superior in almost every aspect, because the program was originally made for Linux.
My personal opinion on Linux is that it's a very nice OS, but it's not for me, because a lot of the programs I use are Windows only. However, Linux does have its own version for programs like an email program, media player, and other applications. I don't use it because like I said, I use mostly Windows programs, and my laptop was free and it came with Vista, and Vista has been working flawlessly for me for 2 years. I am already used to the Windows set up too.
What you should do is... download pendrivelinux, it's a version of Linux that you can run through a USB thumb drive. You can download the version that is a full boot version, or you can do what I do... I have a version that can run while I'm using Vista or XP, great for using on a public computer, because it's like having your own computer, on another computer lol.
So yeah, it's all a matter of preferences. Hope this helped man.
EDIT: I forgot to mention... because the majority of people use Microsoft operation systems, hackers tend to target Microsoft systems and the occasional Apple system (yes, Macs ARE hackable, trust me) but if you have the right anti-virus and anti-spyware, and a working brain (no downloading from shady sources), you won't get viruses. With Linux, it's pretty much impossible to hack at the moment. There have been hacking competitions to see who can hack Linux, and it hasn't been hacked (yet). This is because not many people use it, so not a lot of information regarding hacking Linux is out there, therefore hackers won't bother trying to hack it, unless they're a very dedicated hacker. So in the field of security, Linux is superior to Macs and Microsoft systems.