The House of Commons is a debating chamber where the country's elected representatives fight on the political battlefield.
It hosts scrutiny of all UK legislation - except on policy areas that have been devolved to the institutions in Scotland, Wales or Northern Ireland.
Although it is technically the lower House of Parliament (the House of Lords is the upper), the government draws most of its senior ministers from members of the House of Commons.
Government ministers can be called to justify their policies, actions and omissions in the Commons by backbenchers at departmental question sessions or in time allotted to questions after ministerial statements.
The House of Commons also stages an opportunity for MPs to hold the prime minister to account at a weekly 30-minute question session.
At such sessions, and during debates on controversial matters, the Commons Chamber can become very crowded as it is not large enough for the current number of MPs - there are only 427 green leather seats for 646 MPs.
MPs have special privileges in the House - for example they cannot be sued for libel for anything they say in Parliament - but they are also governed by special rules.
Commons procedure falls under the authority of the Speaker. The day-to-day management of the House is the responsibility of the Serjeant-at-Arms.
A government must command the support of a majority in the Commons if it is to function and survive.
The term "House of Commons" is often used to describe the building where the Commons convenes.
In fact, the Palace of Westminster, as it is officially called, is the magnificent 19th century building on the north bank of the River Thames where both Houses of Parliament - Commons and Lords - hold their sessions.
The House of Lords has a separate debating chamber within the building.
The Palace of Westminster survived the attempts of Guy Fawkes to blow it up in 1605, and even the bombing of the Blitz could not raze it to the ground.
However, the Commons Chamber was not left unscathed by World War II. The Chamber of the House of Commons was destroyed by bomb damage and rebuilt after the war. The current Chamber was first used in 1950.
The great fire of 1834 destroyed much of the original palace. But architect Sir Charles Barry and interior designer Augustus Pugin designed the present day Palace of Westminster which was constructed between 1840 and 1852.