A peso is the basic unit of money used in several countries, mainly in Latin America and the Philippines. Just as Americans use dollars and Europeans use euros, people in Mexico, Argentina, Colombia, Chile, and the Philippines (among others) use pesos to buy groceries, pay for movies, and save for things they want.

The word comes from Spanish and originally meant “weight,” because early pesos were silver coins valued by how much they weighed. Spanish pesos were so widely used for trade that they influenced money systems around the world. In fact, the American dollar sign ($) comes from symbols used for the Spanish peso.

Different countries have different peso systems that aren't interchangeable. A Mexican peso isn't worth the same as an Argentine peso, just like a Canadian dollar differs in value from an American dollar. If you traveled to Mexico City with 100 pesos in your pocket, you could buy snacks and souvenirs, but those same pesos wouldn't work in a store in New York or London. You'd need to exchange them for local currency first.