Referéndum vs. plebiscito
In Spanish, both referéndum and plebiscito refer to direct popular votes, but they are not interchangeable. The fundamental difference lies in what the public is asked to decide on: a specific legal norm or a broader political decision.
Referéndum
B2A referéndum is a direct vote in which the electorate is asked to approve or reject a specific law, constitutional amendment, or other normative text. It is a consultation about a specific piece of legislation that has often already been debated or created by a legislative body.
El país celebrará un referéndum para aprobar la nueva constitución.
(The country will hold a referendum to approve the new constitution.)
Se necesita un referéndum para ratificar el tratado internacional.
(A referendum is needed to ratify the international treaty.)
El gobierno convocó un referéndum sobre la reforma del sistema de pensiones.
(The government called a referendum on the pension system reform.)
Los ciudadanos votaron en contra de la ley en el referéndum del domingo.
(The citizens voted against the law in Sunday's referendum.)
Plebiscito
C1A plebiscito is a direct vote where citizens are asked to show their support or rejection for a specific political policy, a decision by a ruler, or a fundamental change of sovereignty, such as territorial changes. It is often a vote of confidence in the government or a major political direction.
En 1988, Chile tuvo un plebiscito para decidir la continuidad del régimen militar.
(In 1988, Chile held a plebiscite to decide the continuity of the military regime.)
Se realizó un plebiscito para consultar al pueblo si querían una monarquía o una república.
(A plebiscite was held to ask the people if they wanted a monarchy or a republic.)
La región votará en un plebiscito para decidir si se independiza del país.
(The region will vote in a plebiscite to decide whether to become independent from the country.)
El presidente sometió su política de paz a un plebiscito nacional.
(The president submitted his peace policy to a national plebiscite.)
Summary
In essence, a referéndum is a vote on a specific text (a law, a constitution, a treaty), asking the question Do you approve this norm?. In contrast, a plebiscito is a vote on a major political action or decision (a change of government, a territorial shift, a fundamental policy), often asking the question Do you support this political decision or leader?.