The system of government is called “democratic” because the government is elected by the people themselves every five years, everybody in Jamaica aged 18 or over having the right to vote. This is called universal adult suffrage. The Parliament or Central Government consists of Her Majesty, a Senate and an House of Representatives. The Queen is represented in Jamaica by the Governor General, who is appointed by her on the recommendation of the Prime Minister.
The Senate consists of 21 persons, called Senators, all appointed by the Governor General on the advice of the Prime Minister and on the advice of the Leader of the Opposition. The Senators between themselves choose a chairman who is called the Speaker.
The responsibility of Parliament/Central Government is to look after the welfare of the island and its people. It makes the laws and handles the finances of the country. In the maintenance of law and order, parliament is assisted by the Judiciary (that is, the Courts), the Police Force and by the Jamaica Defence Force and other military units in regard to the defence of the island.
The principal instrument of policy-making is the Cabinet which is charged with the general direction and control of the Government of Jamaica and whose members are collectively responsible therefore to Parliament.
The Cabinet is comprised of a Prime Minister, appointed by the Governor General from the members of the House of Representatives, along with no fewer than 11 other members, all appointed by the Governor General on the advice of the Prime Minister, from among members of the two Houses, no fewer than two and no more than three such ministers being members of the Senate.
For more see Office of the PM