What is the difference in usage of fuera and afuera?
When do you use fuera as opposed to afuera? Does one function as a noun as opposed to adjective, etc. Are there differences in the nuances of meaning?
Fuera is outside and away afuera is outside
They are adverbs, they mean the same, so you do not use them ´as opossed´. The difference is one of usage.
«Está fuera» and «va afuera» are both grammatically correct, although depending on the region there might be an informal use of one for the other in the first case
afuera as a noun is use in the plural form meaning the surroundings, outskirts.
Ella vive en las afueras de la ciudad - She lives in the outskirts of the city.
You can also find that fuera is followed by the preposition de while afuera is never followed by it:
The restroom is outside the house
El baño está fuera de la casa = El baño está afuera.