Portion of a physical disk that functions as though it were a logically separate disk. After you create a partition, you must format it and assign a drive letter to it before you can store data on it.
A partition is often called a volume, however a partition is more than just a volume. For example, an extended partition can contain several volumes, but a volume cannot contain partitions.
The main difference between a partition and a volume is that a partition is just a part of the disk space (it doesn't know what is located inside it). However, a volume does contain a particular file system, disk letter, etc...
A volume may be a primary partition or a logical drive in extended partition.
On a software RAID-type disk, a partition is called a dynamic volume.