What exactly does "Ubuntu" mean?
The word "Ubuntu" is African. It means "Humanity to others" or "I am what I am because of who we all are." The people behind the Ubuntu operating system believe Ubuntu accurately describes what they are trying to do.
Why should I get Ubuntu?
If being free isn't enough, Ubuntu gives you much more performance than Windows. Ubuntu is also more secure (although this is because people who make viruses and spyware are primarily focused on Windows). Ubuntu will also install alongside Windows if you want it to; Ubuntu even comes in the form of a Live CD, which means that you can try Ubuntu on the CD without making any changes to your computer.
Is Ubuntu A True Windows Replacement?
That would depend on what you use Windows for. In most cases, Ubuntu can do the things that Windows can. For example, you can play all types of media, do all your "office" work (word processor, spreadsheet, database, etc.), browse the Internet, edit photos and videos, and more. However, one place that Ubuntu (and Linux) in general can use some improvement in is games. If you are a serious gamer, you should look into more detail about how games work in Ubuntu and whether the games you play will also play in Ubuntu (or if there's anything you have to do to make them work). In short, Ubuntu does most of the things Windows can. You can find out for yourself by trying the Live CD without making any changes to your computer.
How Can I Get Ubuntu?
The most popular way to get Ubuntu is to download it and burn it to a CD. Just download the file, and use a program like ISO Recorder to burn the file to a CD.
If you don't have a CD burner, you can order the CD. There are two options here. You can buy a CD, or you can request free CDs. While requesting free CDs might seem like the better option, they can take up to 10 weeks to ship, so it's recommended that you either burn your own CD or buy one.
Now What?
Now that you have the Ubuntu CD, you can boot into the CD and start using Ubuntu. The instructions vary per computer, so please see this article (not up yet) on getting Ubuntu installed on your computer.