actually, Enterpriser, its an operating system, not just a kernel, (well at least it used to be considered a full operating system) but calling the linux kernel just a kernel is like denying that MS-DOS was never an operating system, even though dos stands for disk operating system.
it started out when a guy named linus (forgot his last name) changed Unix, a command-line operating system similar to MS-DOS, and called it Linux, at this time it was still command line. since then people have given it a graphical user interface, GUI using desktop environments such as Gnome and KDE, and there are hundreds (if not more) different linux distrobutions out there, so try them out on liveCD if you decide to try linux them before putting them on your harddrive.
good things about linux:
almost no viruses (only a couple for linux server O/S's)
in my opinion, most distrobutions are a lot faster than windows, and can run on way less resources.
ITS FREE!!!
is that a good enough explanation?