The Cabinet consists of the Prime Minister and Ministers who have been appointed by the Governor General on the advice of the Prime Minister.  Virtually all members of Cabinet are Members of the House of Commons, with one or two Senators also appointed.  The Cabinet is the head of the executive branch of government, although its role in theory is to formally advise the Governor General. Individual Cabinet Ministers are responsible for a government department or portfolio, but collectively the Cabinet makes decisions on behalf of the Government, decides what legislation to introduce,  and is responsible to Parliament for the conduct of the government. The members of the Cabinet remain in office until they resign or successors are appointed. Traditionally, Prime Ministers have tried to ensure that the cabinet reflects the different regions and diverse composition the Canadian population. 

A Parliamentary Secretary is appointed by the Prime Minister to assist a cabinet Minister, or, in some cases, to assist several cabinet Ministers or the Prime Minister.  A Parliamentary Secretary works under the direction of the Minister, and has parliamentary and departmental duties. A Parliamentary Secretary functions as a liaison between the Minister and Parliament and the government caucus. He or she plays a key role on parliamentary committees that are responsible for the issues relating to the department. The Parliamentary Secretary may table documents in the House of Commons or answer questions on behalf of the Minister, but may not present Government Bills. On occasion, a Parliamentary Secretary may represent the Minister at public functions, and may be given policy-related duties, although the Minister retains ultimate responsibility. 

An Opposition Critic is an opposition party member who is given responsibility for scrutinizing and critiquing the administration and policies of a particular department or portfolio. An opposition critic is the chief spokesperson and advocate for the policy area to which he or she is assigned in the House of Commons, in its committees, and in the media. An opposition critic will also help develop his or her party’s position and policies in the area. Collectively, a party's opposition critics are sometimes said to form a shadow Cabinet.