As used in this act:

    (a) "Public body" means any state or local legislative or governing body, including a board, commission, committee, subcommittee, authority, or council, that is empowered by state constitution, statute, charter, ordinance, resolution, or rule to exercise governmental or proprietary authority or perform a governmental or proprietary function; a lessee of such a body performing an essential public purpose and function pursuant to the lease agreement; or the board of a nonprofit corporation formed by a city under section 4o of the home rule city act, 1909 PA 279, MCL 117.4o.

    (b) "Meeting" means the convening of a public body at which a quorum is present for the purpose of deliberating toward or rendering a decision on a public policy, or any meeting of the board of a nonprofit corporation formed by a city under section 4o of the home rule city act, 1909 PA 279, MCL 117.4o.

    (c) "Closed session" means a meeting or part of a meeting of a public body that is closed to the public.

    (d) "Decision" means a determination, action, vote, or disposition upon a motion, proposal, recommendation, resolution, order, ordinance, bill, or measure on which a vote by members of a public body is required and by which a public body effectuates or formulates public policy.