Some background:

Word: The term comes through Middle English and Old French from a Latin root, prorogare, to prolong.

Effect: Prorogation essentially ends a session of Parliament, allowing for a new beginning with a speech from the throne.

Length: Prorogation can be as short as a few hours, or as long as several months. During this period, the House of Commons and Senate are shut down but the government remains in power and MPs remain MPs.

Frequency: Most Parliaments are prorogued at least once and often there are several prorogations and sessions in the life of a Parliament.

Authority: Prorogation is ordered by the Governor General on the advice of the prime minister. As one expert put it: “It's not covered by statute law at all. It's a personal legal power of the Governor General and by convention the prime minister has the right to advise on that. And by convention it's actually the prime minister's decision.''

Ceremony: At one time, prorogation was done in a formal ceremony in the Senate chamber, but that hasn't been used in almost three decades. A simple proclamation signed by the Governor General does the trick today.

Current Parliament: Prime Minister Stephen Harper has twice asked for prorogation in this Parliament, once in December 2008 and again last month.

Critics: The opposition says Harper misused prorogation power to dodge defeat in 2008 and to avoid committee scrutiny of Afghan detainee policy this year. But Harper says it's time to take stock and consult Canadians before starting afresh with a throne speech.

How soon: Prorogation is routinely granted. Governor General Michaelle Jean took a few hours before granting prorogation in December 2008, but that was a tricky case, because opposition parties were threatening to defeat the government and install a coalition government just weeks after the last election.

Limits: Governments can't use prorogation to shut down Parliament indefinitely. In the first place, that would violate the constitutional requirement that Parliament meet at least once every 12 months. And without Parliament to approve a budget and spending estimates, the government would run out of money.

Legislation: At one time, prorogation killed all legislation before Parliament, but rule change in recent years provide that most bills can be revived in the new session at the same stage they were at when the previous session ended.