Translators are marathon runners and interpreters are sprinters.
If I had to explain the difference between a translator and an interpreter to someone who doesn't know anything about our job, I would use this metaphor.
Translators must reflect on every single word, patiently file and chisel the text until they are satisfied with the result.
Sometimes it takes them an hour to translate a word and they do lengthy research for certain texts.
Interpreters, on the other hand, have to act quickly and be very precise in the short time they have available, respecting the vocabulary of a given field.