Quebec is the largest province in Canada, covering most of the eastern portion of country. The St. Lawrence River is in the southern part of Quebec, and connects the Great Lakes to the Atlantic Ocean. This area, the St. Lawrence River Valley, is the most populated area, and that's also where the capital city of Quebec City is located, as well as the largest city, Montreal.
Although Quebec is technically a Canadian province, over the years Quebec has shown a desire to become a sovereign nation, but has thus far remained part of Canada. But nonetheless, culture is important to the people of Quebec, and part of this is shown by the fact that French is the official language, although the dialect is a bit different than European French, and is known as Quebecois French. It is important also to note that while they are part of Canada, and have French heritage, the people of Quebec have their own identity, and comparisons to the people of France or the rest of Canada can be a touchy subject.
When visiting, don't ever assume that everyone automatically speaks English. Also, keep in mind that most signage will be in French only.