Hola Jasmine! Well, I'll try to explain you the difference. The main difference between "pretérito imperfecto" and "pretérito indefinido" is the action in the sentence. The point is, with "indefinido", the story progresses. Using "imperfecto", you can explain the circumstances around an action, but the story doesn't progresses. For example: (Indefinido) (In this case, the story has a progress and a final) - When I finished my work, I went home immediately. - Cuando terminé el trabajo, me fui a casa inmediatamente. (Imperfecto) (In this case, you explain the circumstances around the action, but there's not a progress). - After doing my work, I used go home immediately. - Cuando terminaba el trabajo, me iba a casa inmediatamente. As you can see, using Indefinido, you can tell the past around an specific point in time. Imperfecto also explains the past, but there's not a specific point in time. I hope this can help you, if you have a doubt please tell me! Saludos.