From my understanding, there are three types of visa: vistor, student and business.
Vistor is the simplest one. Once you entered Canada, the plastic entry visa is not valid anymore, but by default, you have six month to stay.
As a student, you need a student permit, still once you entered Canada, the plastic thing on your passpart is not valid anymore if it's a single entry visa (usually it's). If you student permit is valid, then you're ok to stay. But if you want to go back to China and come back again, then you need another entry visa ( I think, never tried before)
Business is out of our interest.
Just my 2 cents.