Depending on your citizenship, you may require a Temporary Resident Visa to enter Canada. This document is also called a TRV or an entry visa. A TRV is different from a study permit: it is used to enter Canada, while a study permit allows you to remain in Canada. TRVs are often issued for the same length of time as the study permit. If you have a study permit, a TRV is not needed while inside Canada, but it is a good idea to keep a valid TRV in case of sudden trips abroad.
If you are coming to Canada as a visitor (not on a study or work permit), your valid TRV will allow you to travel to Canada and if admitted, remain in the country as a visitor for up to six months, if you meet other requirements such as criminal, medical and financial matters.