For anyone who doesn't know, Linux (well GNU/Linux or whatever you guys want to call it) is an operating system (like Windows or OSX) and it's great - whatever its called!
What makes it so great you ask? Well... for a start its free as in 'free beer', secondly its free as in 'free speech' and finally its free as in free from ad/spy/malware and virus' etc.!
There are many 'versions' of the Linux operating system, commonly known as 'distributions'. Each distrubuntion may have different software installed by default and/or a different GUI (graphical user interface - typically Gnome, KDE or XFCE but there are many others) and/or a different way of doing things (such as updating etc.).
The distrubution I use is called Ubuntu. Why did I choose Ubuntu? Well there are many reasons but the main reason is that it has a fantastic community and if I ever have any problems I'm sure that I'll be able find the support I need.