Die Wolken ziehen draussen vorbei. The clouds are moving past outside.
Ausserhalb, aussen and draussen are adverbs of place, meaning they indicate where something or someone is, goes or comes from or where something happens.  The difference between these three adverbs are the exact places where they are used.  Aussen is used to show that something is on the outside, on the outer side.  Aussen is the opposite of innen (inside). 
- Die Tasse ist aussen schmutzig. The cup is dirty on the outside.
- Das Auto ist aussen beschaedigt. The car is damaged on the outside.
- Nach aussen hin ist er ein netter Mensch. Outwardly he is a nice person.
- Von aussen sieht das Hotel gut aus. The hotel looks great from the outside.
Draussen is used to show that something is outside of a room, in the open, outdoors, al fresco. Draussen is the opposite of drinnen (inside, indoors).  
- Die Kinder spielen heute draussen. The children play outside today.
- Draussen ist es im Winter frueh dunkel. It's early dark outside in winter.
- Wenn es nicht regnet essen wir draussen. We'll dine al fresco if it doesn't rain.
Ausserhalb can be used as an adverb or as a preposition followed by the Genitive case.
If used as an adverb it translates as outside of, out of town in the surrounding area.
- Wir wohnen ausserhalb. We live out of town.
- Das Pizza Restaurant liefert auch nach ausserhalb. The pizza restaurant delivers also in the surrounding area.
- Er ist von ausserhalb. He is from out of town.
If used as a preposition ausserhalb indicates either place (outside, not within, not in) or time (not during, outside of).
- Ausserhalb der Stadt (fem.) sind die Haeuser guenstiger. Houses are more affordable outside of town.  
- Ich habe viel zu tun ausserhalb meiner Abeit (fem.). I have a lot to do outside my work.
- Frisches Obst ist nicht so lecker ausserhalb der Saison. Fruit is not that delicious out of season.
- Wir sind ausserhalb des Empfangs. We are out of range.
- Die Sekretaerin arbeitet ausserhalb der Geschaeftszeit. The secretaty works outside business hours.
