Por vs para
When and how would which to use?
there are many translations for both of these words depending on the context. But one basic example to help you out would be "yo escribi esta carta para ti" meaning, I wrote this letter for you. And then "La carta fue escrito por mi" would mean, the letter was written by me. In this context "para" means for, and "por" means "by". So you can not interchange these two words. But like I said, there are lots of other translations of these two words depending on the context. Hope that helps.