The relevant document is the Linux partition HOWTO:
I won't say too much here since all that is covered in the document but the gist is that Linux auto-detects all the disk partitions and you can find out what they are by using fdisk or looking at the virtual file /proc/partitions.
For regular IDE drives you will find the drives on the primary cable are /dev/hda and /dev/hdb. The one on the secondary and the DVD are then /dev/hdc and /dev/hdd. The first partition on the first drive is /dev/hda1. DVDs do not have partitions so there will not be a /dev/hdd1 - you get the idea.
You format partitions with the mkfs command (Linux supports many file system types).
The list of drives registered to be mounted on the system is in /etc/fstab.
The command 'mount' will tell you about the currently mounted disks.
Hope that was useful,