The difference between the past and the imperfect is that when you conjugate a word into past tense, you're saying that you have already done something, or something has been completed in the past
Imperfect tense pretty much means that something did not have a definite starting point or ending point
Examples
Past tense; Hable con ella ayer
( I spoke to her yesterday)
Imperfect; Solia saber nadar
(I used to know how to swim)
Not sure If this helped but I hope it did
