The speaker is the presiding officer of the national or regional legislature. The title of speaker varies according to the regulations of each legislature. Generally speaking, the presiding officer of the House of Representatives or the House of Commons is called the Speaker, and the presiding officer of the Senate or the House of Lords is called the Chairman. For example, the British House of Commons, the Speaker of the US House of Representatives, the Presidents of the US Senate and the Australian Senate. Its internal function is to convene and preside over the meetings of the legislature according to the rules of procedure, make decisions according to the rules of procedure, exercise the powers entrusted by the rules of procedure, and ensure the order of the meetings of the legislature. The external function is to represent the legislature to which it belongs. For a unicameral parliament, it represents the parliament externally. However, for a bicameral parliament, the speaker only represents his house.