She attended the fund-raiser 'at the invitation of' the committee chairperson. [=she attended because she was invited by the committee chairperson]
You have a 'standing/open invitation' [=you are always welcome; you are always invited] to visit us any time.
The event is 'by invitation only'. [=only people who have been invited to the event can attend it]
(..) with the biggest party ever. Everybody's gonna be there. Everybody? Everybody. yeah everybody's coming to the celebration i'ma hook you up with the invitation let your hair swing and party with me no bad vibes just love, you'll see do the d-a-n-c-e one-two-three-four fight stick to the b-e-a-t (..)2016 Trolls