Several of the provinces were former British colonies, and Quebec was originally a French colony, while others were added as Canada grew. The three territories are Northwest Territories, Nunavut, and Yukon, which govern the rest of the area of the former British North America.
The major difference between a Canadian province and a territory is that provinces receive their power and authority from the Constitution Act, 1867 (formerly called the British North America Act, 1867), whereas territorial governments have powers delegated to them by the Parliament of Canada. The powers flowing from the Constitution Act are divided between the Government of Canada (the federal government) and the provincial governments to exercise exclusively. A change to the division of powers between the federal government and the provinces requires a constitutional amendment, whereas a similar change affecting the territories can be performed unilaterally by the Parliament of Canada or government.
In modern Canadian constitutional theory, the provinces are considered to be sovereign within certain areas based on the divisions of responsibility between the provincial and federal government within the Constitution Act 1867, and each province thus has its own representative of the Canadian "Crown", the lieutenant governor. The territories are not sovereign, but instead their authorities and responsibilities come directly from the federal level, and as a result have a commissioner instead of a lieutenant governor.