"y" is the usual word for "and". You use "e" when the next word starts with an [i] sound: "Juan e Inez", not "Juan y Inez" Likewise, "o" is the usual word for "or". but you use "u" when the next word starts with an [o] sound: "Juan u Oscar", not "Juan o Oscar"

En español se usa la conjunción "e" solo si la palabra siguiente comienza por "i" o por "hi". Ejemplos: - Mis deportes favoritos son el baloncesto y el fútbol. - Mis asignaturas favoritas son geografía e historia. - El agua es transparente e incolora.

Ej 1: Marta e Inés. We use here "e" because next name begins with "I" and it's difficult to pronounce. Ej 2: Francisco y Marta. We use here "y" because "Marta" doesn't begin with "I" or "Hi" and it's easy to pronounce. It may be difficult to understand but it's for phonetic reasons.