It's an Aussie term used to refer to people living in Australia who are originally from certain countries in the Mediterranean region (such as Greece, Italy, Malta, Cyprus, Lebanon, etc.). It's either used to demean such people or used in humor (depending on the context).
More info here:
http://en.wikipedia.org/wiki/WogBut it isn't just about one's race/nationality. It's also about the attitude that Wogs typically display. Not every Aussie from the Mediterranean region has this "I'm fully sick, mate" kind of attitude. So those are usually never called wogs.
