Well, there's classic Mac OS (Mac OS 1 -> Mac OS 9), and then there's Mac OS X (Mac OS 10.0 -> Mac OS 10.6 (to be released in 2 days)).
If you're wondering what kind of editions there are, like how Windows has Basic, Premium, Ultimate, etc, there are two: Client and Server. Client is what is usually used, but Server is if you need to do special internet related activities, such as hosting a website.
Client is $129 (Leopard)
Server is $1000, I believe (Leopard)
Again, Client is the primary version (it is often just referred to as Mac OS X, not Mac OS X Client), and Server is strictly for computers that need server-like capabilities, so it is often regarded. Many people will say that there is only one version of Mac OS X, referring to Mac OS X Client.
Yes, it is. Any type of MacBook that comes out now is a Mac OS X. The most recent version of Mac OS X is Mac OS X Lion, coming out soon.
The Mac OS series are different versions of Apple Internet capabilities. (like for Windows)
Single multitask
Mac OS 9 is the old version of Mac OS. Mac OS X was completely rebuilt from the ground up. Except some of the programs. The interface and look is different, but things like Disk Utility and stuff are the same. Terminal is a program that never gets improvements so that's the same too.
The main OS for Mac can be found on a Mac when it is switched on. The current main OS is called Mac OS X.
Mac OS X (say Mac OS Ten) is the tenth version of the operating system (OS) that controls a Macintosh computer (known as a Mac for short). The equivalent for some other computers would be the Windows operating system. Mac OS X has been around for nearly ten years and replaced Mac OS 9 which was the last version of what is known as the "classic" Mac OS. Although a few Macs still use Mac OS 9 all Macs sold since 2002 have come with Mac OS X and would now be considered a regular Mac. (See links below)
I have a Mac OS X but I know Mac OS is a computer made by the brand/company, Apple.
You cannot without erasing your hard drive and installing Mac OS 9 from scratch. Even then Mac OS 9 may not run on modern Mac hardware because Mac OS 9 needs the ROM chip to boot. Modern Mac OS X hardware uses EFI to boot the system instead of a ROM chip to boot. Mac OS X v10.0 - Mac OS X v10.4 support Mac OS 9 applications and can run them, you just need to install the Mac OS 9 compatibility program which can be found on the Mac OS X Install CD.
The second name of Mac OS X v10.4.5 is Mac OS X v10.4 Intel.Mac OS X 10.4 was known as Mac OS X Tiger.
Compaired to macs windows are a little cheaper but macs are WAY better
Mac OS X use Mach kernelmore about Mach: http://en.wikipedia.org/wiki/Mach_kernel
You can't unless it's been converted to the Windows version. The Mac OS and Windows OS are two completely different computer languages.