Difference of imperfect subjunctive and present sub.

Question

Hello! I don't quite undersatnd when to use the imperfect subjunctive over the present subjunctive. I've been learning from paralee's videos and I understand when to use the subjunctive, yet I don't know why use the imperfect subjunctive over the present. From the videos, I get it's in the past, but the way it was explained, there seems no difference in the meaning. Could anyone help explain this to me? Please and thank you!

Answer 1

There is an explanation here

When you are talking about the present or future, you use the present, and when you are talking about the past you use the imperfect. If the subjunctive action is in the past with respect to the other clause, you use the perfect form in either case.

Answer 2

In my experience (albeit limited), the imperfect subjunctive is used in Spanish when you or I would use the words "would" or "were" when talking in the subjunctive. It doesn't necessarily have to be in the past tense, but it often is.

For instance....I just used it. "...you or I would use the words..." In this sentence, it should be clear to you that I'm talking about a hypothetical situation as indicated by the use of the word, "would." Further, it should also be clear that I'm not talking in the past tense, indicating that the subjunctive tense isn't exclusively used in the past tense.

...you or I would use the words... ...tú o yo usaramos las palabras...