Calabaza vs. ayote vs. zapallo
While 'calabaza', 'ayote', and 'zapallo' are all Spanish words synonymous to the English term 'pumpkin' or 'squash', they are used in different regions and may refer to differing types of squash.
Calabaza
'Calabaza' is a generic term used in many Spanish-speaking countries to refer to pumpkin, squash, or gourd.
En otoño, las calabazas son muy populares en las decoraciones.
(In autumn, pumpkins are very popular in decorations.)
Ayote
'Ayote' is primarily used in Central America to refer to what Americans would call a 'winter squash'. The term might refer to a pumpkin or butternut squash-like vegetable.
El ayote en miel es un postre tradicional en Centroamérica.
(Sweet ayote is a traditional dessert in Central America.)
Zapallo
'Zapallo' is predominantly used in the Southern Cone countries (Argentina, Chile, Uruguay) and in parts of Bolivia and Peru. It generally refers to various kinds of summer and winter squashes.
La sopa de zapallo es una opción saludable para la cena.
(Pumpkin soup is a healthy option for dinner.)
Summary
'Calabaza', 'ayote', and 'zapallo' are three terms referring broadly to 'pumpkin' or 'squash' in English. However, usage varies by region with calabaza being a more general term, ayote appearing in Central America referring usually to winter squash, and zapallo voiced chiefly in southern South America pointing to various kinds of squashes.