Non-visa Travel Authorization

Under new rules from Citizenship and Immigration Canada, visitors to Canada without a visa may require an Electronic Travel Authorization (eTA).

Quote from http://www.cic.gc.ca/english/visit/:

New entry requirement now in effect

Visa-exempt foreign nationals are expected to have an Electronic Travel Authorization (eTA) to fly to or transit through Canada. Exceptions include U.S. citizens, and travellers with a valid Canadian visa. Canadian citizens, including dual citizens, and Canadian permanent residents cannot apply for an eTA.

Visit Citizenship and Immigration Canada for more details.