Depending on your country of citizenship, you may require a Temporary Resident Visa (TRV) to enter Canada. If you come from a TRV-exempt country, you may still require an Electronic Transit Authorization (eTA) to fly or transit through Canada.
A TRV (also referred to as an entry visa) is a sticker placed inside your passport that gives you permission to enter and re-enter Canada. This sticker does not give you status in Canada. It is not your temporary resident status document (i.e. study permit or work permit).
If you apply for a TRV from outside of Canada, you will most likely be given a single-entry visa which gives you permission to enter Canada once.
If you apply for a TRV from within Canada using your temporary resident status document (i.e. study permit or work permit), you will likely get a multiple-entry visa. Your TRV will typically be set to expire at the same time as your status document. However, the validity period of your visa is determined by the immigration officer reviewing your application. The officer may decide to give you a visa that is valid for a shorter period than your status document.