What is Linux and Ubuntu?

That completely depends on you and what you want and expect from your computer. Your best bet is to try out Ubuntu, which is easy since you can install it without touching your current Windows stuff.

Ubuntu is a distribution of Linux – which itself is a flavor of unix. Currently the most widely used (for desktops/laptops) and supported distro.

http://en.wikipedia.org/wiki/Linux
http://en.wikipedia.org/wiki/Ubuntu_(operating_system)

It’s more than adequate for most office/internet and further tasks. You could give it a try by running the live CD (same as the installation cd). It’s also faster to boot on laptops, and there’s also a version for netbooks – which can save you a lot of time and come handy if you’re a student.

This page has some useful information that will help you determine which is better for you.

Linux is a great OS for lots of power on a laptop or machine with limited drive space. Windows over the years ’‘grow’d like Topsy’’. It’s incredibly bloated, with code wrapped around code wrapped around code. My guess is nobody knows what half of it does, or if it even does anything any longer. Windows relies on the ever exploding size of drives and RAM to avoid the effort of making the OS efficient and slim. Linux is compact.

Ubuntu is probably the easiest distro of Linux to use, but it’s going to take more Googling and nerdiness than just installing Windows and letting Plug-and-play take care of all the thinking for you.

Just to pick a little nit: Linux is not a “flavor of UNIX”. Flavors of UNIX include AIX, Solaris, Mac OS X, HP-UX, etc.

Linux is Unix-like in that it “behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification.”

Linux (when combined with GNU) is an operating system, similar to Windows or Mac OS. Ubuntu is a particular distribution of Linux. It’s the most popular and (arguably) the most user friendly. I recommend just giving it a try. You can download the Ubuntu Live CD from their website. This will allow you to run a fully functional (albeit slow) version of the OS straight from the CD, so you can try it out without making any changes to your computer. If you like it, you can install Ubuntu alongside Windows. This way, you’ll be able to have both operating systems on your computer.

@Ivan That is why I run it from a USB stick on borrowed systems I don’t plan to install Ubuntu on; Flash is quicker than CD.

And to clarify and expand your last sentence, you can either install Ubuntu alongside Windows and do a straight-up dual-boot, or you can install Ubuntu with Wubi, which is easier to do but results in a slight speed hit and less stability.

My old netbook ran Ubuntu (only) since I didn’t feel it worth the hassle of setting up a dual-boot. Installing that way was simpler than installing many Windows programs (I know that I like in the US, speak English, and am in the Pacific time zone, which is all I needed for a full install). My 13-year-old cousin (with limited computer skills) now has that netbook and likes Ubuntu better than the Windows on his family’s PC. He says it’s easier to use in general and especially easier to install stuff, plus he likes not having to worry as much about malware.

@Ivan‘s description is most accurate in that linux is the operating kernel and you need drivers and filesystems and GUIs (GNU) to use it on a desktop.
People have packaged that up in countless variations including Ubuntu, which deserves its popularity for ease of installation and use, and RedHat which can have a bit more for industrial-strength applications, and Puppy linux which can install and run on twelve year old laptop with 256M of RAM and run better than whatever that laptop came with.