A referendum is a direct vote by the electorate on a proposal, law, or political issue. It is a way for citizens to express their wishes with regard to government policy or proposed legislation. A referendum can result in the adoption of a new policy or specific law, or it may be only advisory. In some countries, it is synonymous with and also known as plebiscite, votation, popular consultation, ballot question, ballot measure, or proposition.

Referendums can be classified by different dimensions, such as mandatory vs optional, binding vs consultative, and who initiates them. A referendum can be binding or advisory, and different names are used for these two types of referendums in some countries.

Referendums can be initiated by citizens, the legislature, or certain commissions, depending on the country or organization that takes the initiative to start the referendum process. In the United States, for example, a referendum can be used to allow voters to approve or reject a new law, proposal, or course of action.

Overall, a referendum is a way for citizens to have a direct say in the laws and policies that affect them, and it is an important tool for democracy.