To interpret something is to form an opinion or personal understanding of something. To explain something is to try to make someone understand it. The noun form of 'interpret' is 'interpretation'. The noun form of 'explain' is 'explanation'. Ex. -A single explanation can have infinite interpretations. -Every religious text has millions of interpretations. or: Every person interprets religious texts differently. -If you're explaining something to me, I'm interpreting what you're saying (although my interpretation may not be what you intended). -If you're explaining something, you need to be actively actively telling someone the explanation. To interpret something just requires you to form your believe in your head, and requires no other people. A book can't interpret anything, because it can't think. You could say "The author's interpretation...", in which case it means that the you believe that the author's personal opinion or understanding on the subject is irrational. This entire post of mine is an explanation ie. I've been explaining the difference between 'explain' and 'interpret'. While you read this, you're interpreting what I wrote.

To explain you don't have to interpret but to interpret you might have to explain. Hopefully someone native will give you good explanation.. they will not interpret it for you.. That two words can have completely different meanings and they are very different to replace in a sentence.. unless the context really allow you to.