PO Box vs POB

PO Box and POB both are nouns.

Word	Noun	Adjective	Verb	Adverb
PO Box	Yes	No	No	No
POB	Yes	No	No	No

As nouns, PO Box and POB are synonyms defined as:

PO Box and POB: a numbered compartment in a post office where mail is put to be called for

Other synonyms of PO Box include call box, letter box, Post-Office box.

PO Box (noun)	POB (noun)
a numbered compartment in a post office where mail is put to be called for	a numbered compartment in a post office where mail is put to be called for