When "fdisk" partitions a drive, it essentially splits the drive into two; a Primary Partition and an Extended Partition.
The Primary Partition will be recognized straight away, but the Extended Partition is invisible to Windows, until you do something with it!
Within the Extended Partition, you create Logical Drives. This can comprise of the whole of the remainder (Extended Partition) of the drive, or, it can be further split into a number of Logical Drives according to taste.
So, at its simplest, you create a Primary Partition, (C: Drive) and an Extended Partition, using the whole of the extension as a Logical Drive, (D: Dive).
Or, you create a Primary Partition, (C: Drive) and an Extended Partition, within which you create TWO further Logical Drives, (Drives D: and E:).
The Extended Partition can be sub-divided into what ever you want. In my case, I have chosen to create a Primary and three Logical Drives in the Extended Partition. This is created for my convenience, and I make sure that all my personal files and back-ups are on drives that are NOT C: Drive, hence, if I have to do a re-install (or a Ghost image), all my personal files remain in tact.
Think of it as a number of individual filing cabinets. One gets destroyed by fire (C: Drive) but the others remain unaffected.