A hard drive can be divided into primary partition and extended partitions. Partitions function as physically separate storage units. This allows you to separate different types of information, such as user data on one partition and applications on another. A hard drive can contain up to four primary partitions, or up to three primary partitions and one extended partition, for a maximum of four partitions.
There can be only one extended partition on a hard disk, so you should include all remaining free space in the extended partition. Unlike primary partitions, you don’t format extended partitions or assign drive letters to them. You divide extended partitions into segments. Each segment is a logical drive. You assign a drive letter to each logical drive and format it with a file system.