OK help us Yanks out here.
PM is the head leader in Australia, right?
And she is calling an election for what?
The Prime Minister is Australia’s Head of Government (technically the Governor General and Queen rank above the Prime Minister, but they don’t run the government).
Australia’s system is based on Britain’s - elections must be held within a particular period (about three years for Australia) but the Prime Minister may call one earlier. In this case, the three years expires early next year. If an election is called, all Members of the lower House of Parliament run for election - similar to a Congressional election in the US. The party (or parties in coalition) that win the most seats hold government and their leader is the Prime Minister.
So this election will determine which party governs Australia, and who the Prime Minister is.