Uses and features
The preterit describes the past as a completed action. The preterit may report on past events as complete units of time. It may focus on the beginning, the end, or the entire event.
The preterit can focus on the beginning of an action, for example:
Juan empezó el examen a las 9 am. (Juan started the exam at 9 am)
The preterit can focus also on the end of an action:
Ayer, fui a visitar a Fernando. (Yesterday, I went to visit Fernando)
In the use 3, the preterit can be viewed as aperiod of time as a completed unit of time:
En España la guerra civil duró tres años. / In Spain, the Civil War lasted three years.