Hi Mark. Thanks for your question.
Each year the Australian Government presents a plan for their spending to the Australian Parliament. This is called the Budget and takes the form of bills—proposed laws—called supply bills. Supply bills allocate money to the government to pay public servants and keep services running. If supply is blocked then the government may not be able to continue all services and may have to stop paying some government employees.
In 1975, the opposition deferred voting on supply bills in the Senate in an attempt to force Prime Minister Gough Whitlam to call an election for both the Senate and the House of Representatives. In response, Mr Whitlam decided to ask the Governor-General to call a half-Senate election to resolve the situation. However he was dismissed before this request could be formally agreed to.
More detailed information on the Museum of Australian Democracy website, Dismissal.