There are basically three major computer operating systems: Windows, Mac OS, and Linux. Windows is by far the most widely used, mainly because most computers come loaded with Windows on them. Mac has a decent share of the market, but you can only have the Mac OS if you buy a Mac computer. Linux is popular in the computer programmer scene, but it is only used by a very small percentage of the public. All three have their advantages and disadvantages.
The biggest advantage to using the Windows operating system is that most everyone else uses it, too, so they can answer questions and you can get better technical support. Another advantage is the amount of games that are available to the Windows system. Most game companies target Windows because they have to get special licensing to make games for Mac computers. Plus, Windows is usually more convenient to use because it comes preinstalled on most computers.
Mac computers definitely have their place in the computer system market. In general, they are better quality than Windows computers because all of the programs go through a rigorous testing period before they are released to the public, whereas Windows usually releases programs before they are ready and then releases a series of patches to fix bugs that are found in the system. Mac computers cater better to a graphic design audience, and Windows computers are better for a gaming audience. Both are good at basic computing like word processing.
The Linux operating system is open source software, which means you don’t have to pay anything to use it. You can put it on computers that are currently running Windows if you are unsatisfied with the way that Windows runs. Linux is great because you have a ton of options in your set up.