Region Detail - Difference between USZip5 and Postal Code

When user creates a region, under region details, he can choose Geo Hierarchy USZip5 or Postal Code.

USZip5 is a range and Postal Code is one single code.

Is there any other difference between USZip5 and Postal Code?

When user wants to add one single postal code to a region detail, is it right to say that he can either set Geo Hierarchy to be Postal Code then add the code, or set Geo Hierarchy to be USZip5 then set both Low Range and High Range to the same postal code value?