Linux is an operating system much like Windows of Mac OS but it completely free. However, Linux comes in many MANY flavors (called distributions or distros for short). You know for Windows you have Windows XP pro, Windows XP home and Windows 7 etc...
They all look the same and have slightly more advanced functionality under the hood?
Well in the Linux world, the core is pretty much the same but everything else can be very different between distributions so they will look completely different.
You don't have to learn ANY programming language to start with Linux, you don't even have to erase windows. You can go to distrowatch and pick a distribution targeted towards new users (I'd recommend either Linux Mint or Ubuntu). The best list of current distros is at:
http://www.distrowatch.com
Then you download the ISO file and burn it to a CD and boot from the CD. You should be able to easily use all of the functionality of your computer.
This is a great article for getting started:
http://lifehacker.com/5774997/getting-started-with-linux-how-to-install-linux-on-your-computer
Some main differences between Linux and windows:
1.) Installing software on linux is different than windows. In windows you go to a website download software and install it on your PC, in Linux you use a program called a package manager to manage all of the software for your PC. It will keep all of it update it and handles both installing and removing software (very similar to app stores in Android and iOS devices). The package manager gets the software from something called a repository which keeps all of the software that is available for your distribution of Linux. (not technically true but a good assumption for new users). This means that it is much easier to install software in Linux because you just have to pick your software from your package manager and click install and you're good to go.
2.) Windows programs do not easily work on Linux. You can use a program called Wine to try and run some windows software on Linux but usually the best thing to do on Linux is to use Linux programs. Things like Microsoft Office are replaced with Libre Office, Windows Media player is replaced with VLC media player etc... There are many different programs which are really great and come pre-packaged with your distribution (though you can change them or get new ones via the package manager)
Common replacements are:
Internet Explorer = Firefox/Google Chrome
Outlook = Thunderbird or Evolution
Microsoft Office = LibreOffice or Openoffice
Windows Media Player = VLC, Mplayer
Adobe reader = there are a million and one pdf readers for Linux
3.) Forget about antivirus software, you don't need it for Linux unless you are scanning files before moving them to a Windows machine. There are hardly any viruses targeted at Linux.
I'd suggest you go and try it, it's completely free and easy.
Feel free to contact me with any specific questions.
Hope this helps!