Choosing a Linux Distro
You have made up your mind to install Linux. The question then is where can you get Linux. And once you figure that out, you realize that there's no such thing as a single `Linux' - there are dozens of varieties (distributions) of Linux. That leads to another question -- How does one choose from the many `Linux_distro_' (common jargon for distribution) available in the market?
This is somewhat like asking "How does one choose a car?" You ought to know a few basic things about Linux, just like "engine", "mileage" and "dashboard gadgets" are essential to choosing a car. Discussing these can go deep into geek-land. So, to keep it simple, let's compare a Linux distro to a car.
The kernel is as important to Linux as an engine is to a car. It runs your Linux; doing stuff like helping other programs access your hardware, sharing your computer's processor between various programs and other such. Just like a car's engine, the Linux kernel keeps getting better with new additions like new security features, support for more hardware and hence more bang for your buck. Excellent, considering that the kernel (like Linux) comes absolutely free.
So when you pick a distribution, go for one that offers you a comparatively recent kernel. Though kernel 2.4.1 is out, most current versions of various Linux distributions will give you some version of 2.2.16 or 2.2.17. Don't install any distro that has an older kernel. If you do, upgrade the kernel immediately.
Operating system programs
We compare these to the chassis, gears and transmission in a car. Without them, the engine (or the kernel) wouldn't be of any use to you. These OS level programs (various servers which handle your mail, web and other services, the "LILO" bootloader, etc.) harness the power of the kernel for you.
User level programs
Now that you have all that you need for a basic car (steering wheel, gears, engine, etc etc), you need to find stuff which will give you a great comfortable ride, like white-wall tyres, comfortable leather upholstery on the seats and such. In the case of Linux, stuff like browsers (from the text-based lynx to graphical ones like Netscape/Konqueror), mail user agents (pine, mutt, Netscape), word processors (Star Office, Abiword), text editors (vi, pico, emacs) etc.