To give you more detail, Linux is - at it's core - a multitasking OS similar to Windows with the exception that it's default UI (User Interface) is command line driven, much like the "Command Prompt" or "MS-DOS Prompt" on your Windows machine.
There are add-ons (XWindows for example) that give you a GUI that is similar to what you see in Windows but that interface is not as robust as the Windows GUI. Where Linux shines is as a network server - primarily as a DNS, DHCP, Telnet, FTP, and HTTP server. It is not yet ready for most people to use it as a desktop OS as it is difficult to get it configured correctly without having to "play" with the CLI (Command Line Interface) and without having to tweak the kernel.
People - for some odd reason - seem to equate their philosophy with Linux. You will find that most (not all) Linux advocates absolutely despise Microsoft and any other big 'ol meanie corporation. As a result, their technical opinions of the various Operating Systems and supporting software is usually biased and closed-minded. The same can be said for people who equate Microsoft with their philosophy. It seems that common sense - on both sides of the OS fence - has been tossed out and people have started applying personalities and schools of thought to a collection of ones and zeros. IMHO, their energies would be best spent espousing their philosophy in arenas where it actually makes sense to do so - town halls, talk radio, water coolers, etc. It truly baffles my mind.
Linux is a fine Operating System as is Windows. I have multiple installation of each at home and do not consider one as "the best". It's all a matter of what it is you wish to do with your computer and which product suits your specific needs. For more information on Linux and the various versions thereof, check out Linux.org