What are the differences between the use of the preterite and imperfect tenses in Spanish?

The preterite and imperfect are both past tenses in Spanish. In general, the preterite tense is used to describe actions that took place in the past and are completed, while the imperfect is used for actions that took place in the past but are not completed and have no definitive beginning or end. Another way to explain this is by thinking that in most cases, the preterite is used with specific timeframes whereas the imperfect is used for more general time frames. For example, esta mañana (this morning) indicates the use of the preterite tense while cada semana (every week) signals the use of the imperfect tense. An easy way to understand this is by remembering to use the imperfect tense in the following 4 situations: 1) Repeated actions over a space of time Cada año iba a Londres.2) Actions that were in progress (e.g. something was happening when something else occurred) Comía cuando sonó el teléfono.3) Times and dates in the past Eran las cinco de la mañana. 4) Descriptions of characteristics El chico era pequeño.