Hello! Mary's answer is very good. "Afuera" means outside, outdoors. ( "vamos afuera a hablar" = "let's go outside to talk " ) You can also use it to say: "get out of here!" = " fuera de aquí!" In many occasions it's possible to use indistinctly one word or another. But the local determination (place, location) is more precise in "fuera". Means outside a place or definite limit. "Afuera" indicates the general idea of distance (inside / outside) and can have grades (more, less, much, so out). Maybe these examples help you to understand the difference. " Ana está afuera." = Ana is outside. " Ana está fuera de la casa." = Ana is outside the house. I hope to have helped. Sofía.

The difference is while you're going yo use a complement or not. You say "me voy fuera de aquí" but not "me voy afuera de aquí". If you're using the preposition "de" after "fuera" or "dentro" you must not use de form with a-. The added "a" means nothing by itself. I'm afraid don't know how to explain better. Hope helped.