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Explain to me the difference between Preterito and Imperfecto. Both are past tense, but you use each for different things.
What is Preterite is used for something with a definite beginning and end. It happened, it's done.
Imperfect is used for something that took an indiscriminate amount of time. You can use "Used to _____" or "Was ______ing" in the sentence appropriately.