Here's why it's not a noun or a predicate:
* Noun: A noun names a person, place, thing, or idea. "Invited" doesn't name anything.
* Predicate: A predicate is the part of a sentence that tells what the subject does or is. "Invited" can be part of a predicate, but it's not the predicate itself.
For example:
* The guests were invited to the party.
* "Guests" is the subject.
* "Were invited to the party" is the predicate.
* "Invited" is the past participle verb within the predicate.