After the installation of linux, generally 13 directories are made.  Unlike windows, these directory begins with a / (in windows they begin c:\).  I highly suggest you print this page out as it is very helpful to beginners. The directories and their uses are:

/bin : Used to hold executable files, found all over the file system.
/sbin: Used to hold the supervisors (root) executable files.
/boot: Bootup files like the kernal are stored here
/dev : This folder holds the device driver files here. They are used to represent physical items eg.  /dev/tty1 = communication port 1
/etc : Used to store most of the configuration files for linux. 
/home: Stores all the user home directories here
/lib : Stores the liberies/runtimes for programs
/mnt : Unlike in windows where c:\ represents a drive, in linux, the different drives are stored in /mnt and act like a directory.
/proc: Holds most of the processes happening in the linux system. 
/root: The supervisors (root) home directory files.
/usr : stores user based files
/var : holds constantly changing files like print spools
/tmp : Temporary file folder 

Unlike in Windows, you must manually mount the CDRom drive unless you have a program to do it for you. In KDE, if you click on the cdrom icon, you can mount the cdrom automatically  To mount a CDrom drive use mount /dev/cdrom /mnt/cdrom .  To unmount it, use umount /mnt/cdrom . Try if you must, but you wont be able to get the CDrom out of the drive while it is mounted. New versions of linux have supermount which mount and unmount the CDrom drive for you (like in Windows)