You will require a visitor visa OR an eTA to fly to, or through, an airport in Canada. You will need one or the other, not both. If you are from a visa exempt country, unless eTA exempt, you will need an eTA to enter Canada by air. If you are visa exempt and arriving by car, train, bus or boat, you do not need an eTA or visitor visa. If you are not visa exempt and arriving by car, train, bus or boat, you will need a visitor visa.