In the Linux file system everything is considered a file–even devices, drives and removable media. It definitely is a bit different than what you might be used to in the Windows world, but after a quick rundown (below) hopefully the organization will make some more sense.
The base (or equivalent of C:\) is called the root folder or “/”. The closest equivalent of “Documents and Settings\User” would be “/home”. The “/home” folder stores each users files, settings, pictures, etc. Most of what you do is held within the /home folder. Below is a quick explanation of the rest:
/bin– binary applications (most of your executable files)
/boot– files required to boot (such as the kernel, etc)
/dev– your devices (everything from drives to displays)
/etc– just about every configuration file for your system
/home– locally stored user files and folders
/lib– system libraries (similar to Program Files)
/lost+found– lost and found for lost files
/media– mounted (or loaded) devices such as cdroms, digital cameras, etc.
/mnt– mounted file systems
/opt– location for “optionally” installed programs
/proc– dynamic directory including information about and listing of processes
/root– “home” folder for the root user
/sbin– system-only binaries (see /bin)
/sys– contains information about the system
/tmp– temporary files
/usr– applications mainly for regular users
/var– mainly logs, databases, etc.
I hope this helps. Again, for the most part as a regular user you wont need to bother with the rest of the areas of the system. Occasionally you might need to edit a configuration file in /etc (as you may have seen in earlier posts), but the rest pretty much takes care of itself.