El pretérito en contraste con el imperfecto
Muchas descripciones gramaticales dicen que hay verbos que cambian significado según su uso en el pretérito o el imperfecto. En realidad el significado del verbo no cambia sino que su traducción al inglés cambia.
María conocía los niños en el parque.
María knew the kids in the park.
María conoció a los chicos en el parque.
María met the kids in the park.
At first glance, it looks like the verb CONOCER (to know/be familiar with) changes meaning in the preterit. However, if you think of the imperfect as being “a middle” in the past (Maria was in the middle of knowing the kids in the park; she didn’t start knowing them and she didn’t stop knowing them) and the preterit of being a beginning in the past (María started knowing the kids in the park—the beginning of knowing) it becomes clear that we are just viewing “knowing” in different ways.
This also works for the other verb in Spanish that means to know about—SABER:
María sabía la verdad.
María knew the truth.
María supo la verdad.
María discovered the truth.
In the first sentence, there is no emphasis on when María began to know the truth. She was in the middle of knowing it and the imperfect is used to signal this. In English we have a special verb for the beginning of knowing something (DISCOVER or TO FIND OUT), but in Spanish you only have to use SABER in the preterit to indicate that it was the beginning of knowing something in the past, which is pretty cool even if you don’t think that Spanish grammar is very interesting.