Unallocated space is not partitioned or I suppose you could say not formatted. Free space is unused partitioned space, and you can shrink a partition that has free space. But deleting it deletes the entire partition.
If you are trying to extend a partition into unallocated space, you can do that but you cannot merge two partitions, with Windows anyway.
If you use Disk Management, you can see unallocated with a black top and primary partitions blue.
If you are trying to do something in particular, you could take a picture of your Disk Management window using the snipping tool and attach using the paperclip on the Advance reply window.