What is a study permit?
A Canadian study permit is issued by Immigration, Refugees and Citizenship Canada (IRCC) and authorizes you to study at a Designated Learning Institution (DLI). It is not a visa on its own — most students also receive a temporary resident visa (visa sticker) or an electronic travel authorization (eTA) to actually enter Canada.
You generally need a study permit for any program longer than six months. Short courses under six months may not require one, but it can still be wise to apply so you can extend or work later without leaving the country.