El Pretérito vs el Imperfecto

Porque tenemos dos tensos del pasado - que muchas veces suenan igual en inglés - hay que aprender los usos particulares de cada uno.

El Pretérito

• Acciones completadas en un tiempo definido del pasado
• You could tell when exactly it happened. It is a particular moment in time.
• It may have happened many times in the past, but you are focused on one particular time.

El Imperfecto

• Acciones habituales – en inglés “We used to live…” “They used to play…”
• Acciones en progreso en el pasado – en inglés “I was reading” “He was talking”
• It is very descriptive.
• You're not focused on one particular time or one moment. If I say "I used to play tennis" you don't know when exactly I did or how many times. That's not the point. My focus is to let you know it's just something I used to do. (However, if I then say, "One time, I won a really hard match." i would have to switch to preterit because I'm now focused on that one match.)

These English phrases are good “tests” for imperfect. If you CAN use this wording (either “used to…” or “was doing...”) it’s automatically IMPERFECT.

If we take it in the context of narration in the past, we can associate

• Pretérito = plot
• Imperfecto = setting (includes the time, almost always the weather), description (includes age), background actions that were happening when other things occurred

For a more complete explanation see Yepes Lesson 40. Pretéritos: perfecto simple vs. imperfecto / Imperfect vs. Preterite.

There is also a good video created by Sr. Lee from Durham Tech found in the Video Library tab and shown below.