Ill. Const. art. VII, § 11

(a) Proposals for actions which are authorized by this Article or by law and which require approval by referendum may be initiated and submitted to the electors by resolution of the governing board of a unit of local government or by petition of electors in the manner provided by law. (b) Referenda required by this Article shall be held at general elections, except as otherwise provided by law. Questions submitted to referendum shall be adopted if approved by a majority of those voting on the question unless a different requirement is specified in this Article. (Source: Illinois Constitution.)