Rocket Spanish Community

Could someone please explain the difference, in plain English between the Preterite and the Imperfect Tenses

I could reply in "plain English," but what I think you're asking for is a simple explanation, and frankly I don't know of a good one. Yes, there are generalizations like "the preterite is used for actions that occurred once and are over and done with" or "the imperfect is used for repeated or habitual past actions," but both of those are over-simplifications. If you want to understand the differences between these two past tenses, you need to do some reading. You might try some online sites such as these:
http://www.studyspanish.com/lessons/pretimp1.htm
http://spanish.about.com/library/weekly/aa021599.htm
http://www.bowdoin.edu/~eyepes/newgr/ats/33.htm

Chapter two of Rocket Spanish's Advanced Book (a downloadable pdf file) also contains some discussion of these tenses.

Google can probably help you find other discussions.

As I've said a number of times on this forum, I highly recommend a small paperback book entitled ¡Búscalo!: A Quick Reference Guide to Spanish Grammar and Usage by William M. Clarkson and Guillermo Campos. It offers very clear, straightforward explanations of just about any grammar question you might have, including the uses of the preterite and the imperfect. This book would be my top recommendation. Another very useful book isl Dorothy Devney Richmond's Spanish Verb Tenses in the Practice Makes Perfect series.

I hope you find this helpful. ¡Buena suerte!