This question may have been asked and answered before, but: What does "below/above the line" mean?
In voting terms, there's a line in between the group tickets, and the individual candidates. Voting above the line means you put a "1" next to your preferred ticket, whereas below means you rank all the candidates running in the Senate of your state from 1-110 (in terms of NSW).
To clarify this a bit more. Each party registers an ordering - not merely of their own candidates, but of all the candidates on the ballot. A party can even register multiple orderings, if it so likes. All these orderings are marked "above the line" and a voter can choose to simply mark that he wants to follow the party suggestion. However, if a voter so wants, she may decide to go bellow the line, where all the candidates are listed, and mark her own ranking in any way she likes. Relatively few people choose to do this, as it is, obviously, nightmarishly complicated with 100 candidates, but, given the electoral system, even those few might matter a lot.