Indahlma wrote:
it shows the capacity as 1.36 TB and only 250 MB used.
The 250 mb is the directory and various other hidden files on the disk, that will be used by OSX.
Do I now have 2 partitions?
No.
(I don't even know what a partition is, but it sounds like two separate spaces to store stuff)
You're right. Multiple partitions can be very useful. For most purposes, they're treated like separate drives. Each shows separately on your desktop and/or Finder sidebar.
Each partition takes up a separate, contiguous, part of the physical disk, unlike, say, a folder that can have it's contents scattered anywhere.
Whether you need more than one depends on what you're going to do with the disk. For example, if you plan to use if for Time Machine backups, but also put other data on it, then you should partition it, as TM works best with it's own, exclusive partition.
If you're going to use it for, say lots of photos and music, then partitioning could limit your flexibility.