preterite is ....
To talk about actions completed in the past at a specific time
Triggered by vague words
A completed action
An action that happened while another one is happening
The beginning or end of an action
A series of events in the past
imperfect is ...
To describe habitual past actions and routines
To talk about moods, feelings, desires, descriptions, and intentions
To set the scene or provide background information, telling a story
Words that don't have a reference to a beginning or an end
Describe a condition mental, physical, and emotional
using preterite and imperfect ...
To indicate that one action occurred (preterite) while another was in progress (imperfect)
To report an action (preterite) that took place because of a condition (imperfect) that was in progress
To present an event where the preterite describes the action and the imperfect sets the stage or background for that action