Partitions are allotments of logical space on your hard disk. These allotments or divisions are distinctively independent parts of a whole. They are usually created in order to effectively manage your hard disk for reasons of your own. If you have a large hard drive that you would like to effectively partition, then you can use a helpful utility like Ranish Partition Manager to help you with creating your partitions.
Ranish Partition Manager allows you to create both primary and extended partitions that can be copied and resized. Though its command-line interface, you can simulate with partition tables to evaluate the affects before implementing them on your hard disk. It can easily help you create dual boot environment with multiple, but different operating system or multiple copies of the same operating system.
Ranish Partition Manager is simply a great way to manage your hard disk, as well as experimenting with other operating systems all on the same system.