Interesting question, David. The term of each Parliament may be divided into sessions. When a session of Parliament is formally closed (other than to call an election), it is said to be prorogued. The Governor-General, acting on the advice of the Prime Minister, prorogues Parliament.
When Parliament is prorogued, the Notice Paper, which lists all business that is before the House of Representatives and Senate, is cleared. Debate on some bills introduced in the previous session may be revived in the new session and Senate committees empowered to meet after a prorogation can continue their enquiries.