Outside of choosing which packages, of the many provided by Debian, that you wish to install on your system, the hardest part of any Linux installation is determining how to partition your hard disk drive. The following discussion is an attempt to simplify the problem for the first time user of Debian.
First, what is a partition anyway? Many DOS machines only offer the C: drive as a valid disk device, but many of these machines have D: devices and more! Many times these additional ``drives'' are actually another physical hard drive connected to the machine, but more often they are not. Many OS installations (and even some Linux distributions) simply consume the physical disk device in one large chunk, called a partition. This single partition gets formatted with the desired file system and then sub-directories and files can be created within that file system.
Using partitions it is possible to divide one physical device into several partitions, and assign each partition a unique device name. In DOS these would be C:, D:, E:, etc... In Linux these are called /dev/hda1, /dev/hda2, etc... for the first physical IDE device on the system and /dev/hdb1, /dev/hdb2, etc... for the second physical IDE device.