when do you use the imperfect and preterite tenses

The imperfect tense is used for actions that were repeated in the past or to describe a state in the past. eg. when I was younger I used to dance - cuando era pequena bailaba. the preterite tense is used when you are talking about a completed action in the past and can put a specific time to it. eg. last weekend I played football - la semana pasada jugue al futbol.