Spanish languge tips for learners: Pretérito versus Imperfecto
Think of Pretérito as a tense for specific actions, events or for enumerating a series of actions.
For example:
Anoche cenaste con tus amigos. Last night you (familiar, singular, tú) had dinner with your frineds. ¿Cuándo visitaron Ustedes el museo? When did you (plural) visit the museum? Yo no comí mucho. I did not eat a lot. Recibí una carta ayer. I received a letter yesterday. Primero me duché, después me vestí, y luego salí. First, I showered, then I got dressed and, after that, I left.Hubo un incendio aquí la semana pasada. There was a fire here last week. Ella fue a Caracas dos veces. She went to Caracas twice.
Think of the Imperfect Tense for ongoing situations, descriptions or underlying conditions. Also it is used to convey habits in the past (in English the equivalent: “used to + infinitive”)
For example:
Había mucha gente en la fiesta. There were many people at the party. (descriptions or underlying conditions) El cielo estaba nublado. The sky was cloudy. (descriptions or underlying conditions) Mientras los niños jugaban yo los observaba. While the kids were playing I was watching them. (ongoing situations) Cuando eramos niños veíamos los dibujos animados después de hacer la tarea. When we were children we used to watch cartoons after doing homework. (habits in the past) Cuando mi abuela era jóven las mujeres tenían menos oportunidades. When my grandmother was young women had fewer opportunities. (descriptions or underlying conditions) La calle estaba sucia. The street was dirty. (descriptions or underlying conditions)