This article won't attempt to advocate the use of Linux over Windows or vice versa. I will try to present the differences and similarities between Linux and Windows in a fair way.
Overview:
Both Linux and Windows (2000, NT, XP, Vista) are operating systems. Linux was inspired from Unix, while Windows was inspired from VMS.
While no single company "owns" Linux, Windows is owned by Microsoft. Various distributions (often referred to as "distros") of Linux come from different companies (e.g. Red Hat, Novell SuSE, Mandrake etc.), while all Windows flavors (95, 98, 2000, XP, Vista) come from Microsoft.
Both Linux and Windows come in Desktop and Server editions.
Cost:
As far as cost is interested, Linux is very cheap or free. I used the word "very cheap" for enterprise users. While anybody can download, install and use Linux, the distribution companies usually charge for technical support.
Windows is expensive. You first pay for the copy of the software and so again for the technical support if you ever want it.
There is additional catch though; Windows enforces you to use a single copy on a single computer. This is not the case with Linux though, once you purchase Linux, you are able to run it on an unlimited number of computers.
GUI:
Both Windows and Linux are GUI based operating systems.
I'm afraid but, Windows has better GUI than Linux and it will get far better with the upcoming Windows Vista release. Linux has two GUIs: Gnome and KDE. Linux is fast catching up and is evolving from a server operating system to a desktop operating system.
Command Line:
Both Windows and Linux comes with command line interface. Windows calls it the "DOS prompt", while Linux refers to it as the "shell". Linux's shell is far more superior than Window's DOS prompt. it is able to do a whole lot of things that are not possible in Windows. Linux support various command line shells such as BASH, Bourne, Korn, C shell and a lot of other.
Third Party Application Software Availability:
Both Windows and Linux run third-party applications. Windows, equated to Linux, has far greater number of third party applications accessible for use. A program written for Windows won't run under Linux (although it is able to be made to emulate, but it'll be very annoying and hence not recommened).
Linux's application pedestal is, even so, increasing threefold. On a more close examination, the average computer user applies the following applications 90% of the time: Word Processor (Office suite), E-mail client, Web browser, Media software, and Instant Messenger. Linux has all these applications and in fact has a lot of flavors for each.
Like Linux, all third party applications are very cheap or free. Whereas, Windows applications can cost a leg and a limb.
Security:
Simply put it this manner, Windows is not secure. If you are using Windows and do not have Antivirus, Anti Spyware, and firewall (memory and resource eating applications), your computer can get affected by a virus in less than 10 minutes. I remember restoring a fresh copy of Windows XP on my Toshiba A40 notebook. I was browsing the Internet with Microsoft Internet Explorer and my machine got infected with loads of spyware in less than 15 minutes!
Microsoft came up with Firewall and Anti Spyware products, but these programs run in the background and eat up your computer's precious memory.
Linux, then again, does not have these issues. I'm not well knowledgeable of any spywares for Linux. One can safely run a Linux distro without ever worrying about installing Anitvirus or Anti-Spywares.
Windows also has more security blemishes than Linux. By security flaw, I mean a hacker can compromise the Windows operating system and break into your machine and destroy your files. But, blemishes on Windows are quickly fixed and patches are often made accessible almost instantly after the flaw is reported.
Supported Hardware: