Any person who wishes to visit Canada will usually need to obtain appropriate authorization from Immigration, Refugees and Citizenship Canada (IRCC). This means applying for and receiving an electronic Travel Authorization (eTA), or a Temporary Resident Visa (TRV) (also known as a visitor visa) before booking a flight to Canada.
This article will help you find out in which category you are, either (i) no TRV nor eTA needed, (ii) an eTA is needed, or (iii) a TRV. As a quick comparison, an eTA is way easier, cheaper and quicker to get than the TRV.
If you are a citizen of a visa-exempt country and travelling to Canada by air, you have to request an electronic Travel Authorization (eTA). Go to this page to see how to get an eTA.
If you are from a visa-exempt country, you only need your passport if you are travelling to Canada by car, bus, train or boat (no eTA needed).
If you are not a citizen of a visa-exempt country, you will need to get a Temporary Resident Visa (TRV) before entering Canada. Go to this page to see how to get a TRV.