The referendum is the right of citizens to approve or reject a law that their legislature has enacted. If a requisite number of citizens sign and submit a petition to their government during a specified period before a law becomes operational, then it is placed before the voters in an election. If a majority votes against the proposition, then the law is rejected.
In some democracies, amendments to the constitution cannot become operational unless they are approved by a majority of the citizens in a countrywide referendum. The rights of initiative or referendum are included in the constitutions of some parliamentary democracies. For example, . . .[t]he constitution of Estonia provides the right of referendum in Article 105, which says, The Riigikogu [parliament] shall have the right to put draft laws or other national issues to a referendum.
The decision of the people shall be determined by the majority of those who participate in the referendum. A law which has been adopted by referendum shall be immediately proclaimed by the President of the Republic. The constitutions of many democracies, including that of the United States, do not include the rights of initiative and referendum. However, more than half of the 50 U.S. states have constitutions that provide either the referendum or initiative or both of these procedures.
By John Patrick, Understanding Democracy, A Hip Pocket Guide (Oxford University Press)