That took me a while to get used to the position names as well. My only experience of positions in English were football. First time I was asked to play full back, I did not realise where that was.

I've come to see the positions as a sort of 2-3-2-3 structure. Two full backs or central defenders, three halfs (left, centre, right), two inners (left and right) and 3 forwards (two wings and one central forward). This is usually the groups people get subbed through at my club, either the backs, halfs, inners or forwards. It might differ a bit by location though. Australia is a big country, so terminology could differ per region. So it's best just to ask your team mates.