Imagine if you went to the ford dealership and bought a car. This car would last you a decent amount of time. It may even impress you at first, but it is known to have problems, the drive train breaks after so many miles, the tires wear out faster, the interior wears out quicker and so on. But it is a popular car and parts are everywhere and everyone knows how to fix them so you keep driving Fords. Just like most people keep using Windows.
Until one day, you pass by the import shop, you see a classy little sports coupe. This is a Porsche. the car is fast, it's sleek, been around for years and only gotten better. But when it breaks down, it breaks. It has issues and there are less mechanics that can fix it. Parts cost more, and are harder to find. This is an Apple computer.
Then as your driving around you see a car you have never seen before, you follow it to the guys house and you ask him about it. He tells you it's a kit car. It has a Porsche engine, a Ford suspension, and a body that was hand made out of fiberglass. It's sleek, it's fast, it is a great car. You ask if you can buy it, the guy says no, but he has a few others in his garage that he has been working on, not all them are the same, many have different drive train, varied engines, electrical systems from all over,most parts are hand made by different groups of people. You get excited cause they all look great, even if your unfamiliar with them. The guy then hands you the keys and tells you to take one for a test drive, he has filled up the tank and won't cost you anything,( Live Cd's ) he even offers to take care of your car while your out and give it a tune up (Open source based testing tools such as Hirin's Boot Cd ) You agree and take out this car that the owner called an Ubuntu. This car is fast, it's sleek, it does everything you want it to, it is familiar, but at the same time exotic. You get back to the guys house and sure enough you pick up your car and it's running better then ever, you offer to pay the guy and he says it's not necessary but if you want to help out give out his business card so more people can hear about it, you agree and drive off. the next day you are driving around and you keep thinking about that drive you took and how much you liked it, so you head back over to the guys house (Let's call him Linus ) Linus is happy to see you and offers you a drink when you get to his place. You start asking him again about how much it would cost to drive one of his cars. he looks at you and before you can say anything he tosses you the keys to a sleek looking coupe right out front. You again ask how much, he laughs and tells you to take it, he will have your car dropped off at your house and there was no charge for any of it. You now own your original car, and now you have this sleek new car that you just got for free. He even handed you enough gas coupons to cover you and let's you know whenever a new engine comes out, new electrical, new interior to come back and he will upgrade it all for free. You ask about if it breaks down and he tells you about your neighbor that built the seats, and your friend that worked on the lights, and about all the others that helped contribute to building the car and let's you know where other owners meet, many of whom have figured out how to work on various parts of this car. While there are not many shops that can fix it, there are many people out there that can help you work on it.
So you drive your new car home, it's different, some people like it and you take them over to Linus' place and he offers them the same deal, others hate it and are satisfied about the cars they already own (even the ones driving the 14 year old Xp edition Tauruses). So while most people go out and buy ford's and others spend a bit more on their Porsche, you get addicted to your Ubuntu, you evn try out some of the other cars and trucks, and semi's and flat beds, and find out that some are easy to drive, others are Arch beasts. But in the end Linus lives up to his promise and continues to upgrade your car every time something new comes out, and he never asks for a dime, your friends and colleagues continue to support each other, your neighbors still make fun of you while they are broken down on the side of the road waiting for an (IT)tow. and your Porsche friends continue to look down on you for not listening to them as they speak to their geniuses on how to operate the radio.
This is open source and why it's important, it's community driven, free, and can run on anything.