Help With The Definition "Franking".

I hope this is the correct area for this, but what is "franking" / "franked"/ "unfranked"...........I have noticed this term referred to in the kiloware section and in my Scott catalog for the $2 prexie scott# 833 it says single franking on cover.....
I did see the glossary but I still am not sure what "franking" or "unfranked" is.
Thanks,
Robert

Stamp Smarter Illustrated Glossary
A marking on a cover, other than a stamp, that indicates that the postage has been paid.
Don

What Scott is also referencing is that certain Presidential issue stamps can be quite valuable when correctly used as a single franking.

An example would be one of the higher values correctly paying the, I dunno, quadruple air mail rate to West Africa or something of that ilk and not making up some big rate on part of a parcel.

Askphil:

Frank:
1: a stamp, mark or signature that indicates payment of postage on a piece of mail.
2: mark on a cover which is authorized to be carried without postage charge due to position of sender; see Free frank.
3. currency unit of Albania.

Franked mail:
1: mail sent without postage prepayment by various officials.
2: a type of prepayment as in "folded letter franked with pair of 5¢ Franklin 1847."
2: Currency overprint on fiscal issue, Surinam, postally valid.
Franking: any postal payment with or without stamps.
Franking privilege: right of government officials to send letters and packages free of postage.