In its most simple form, to call someone huevón, it has two distinct contexts - friendly and not friendly. If you say it to a friend, in a fun manner, you are calling someone "dude." If you are saying to someone who is being a jerk, you are calling them an asshole. It comes down to tone, which is something we all understand. You can say, "Que pasa, huevón?" (What's happening, dude?) or "Que pasa, huevón!" (What the eff, dude!)
If, on your first trip to Chile, you can master these two uses, you are doing well. But it gets much deeper! Chileans love to change nouns into verbs and adjectives. Huevón has been adapted into more forms than I can count. Here are some of my personal favorite:
Puta la huevada: Shit!
Qué huevada? What's happening? (As in, I don't understand what's going on.)
Huevear: a verb meaning, "to goof off."
There are multiple resources for deeper investigation into this fine word. How to Survive in the Chilean Jungle, by John Brennan is a personal favorite. Nos vemos en Chile, huevón!