Starting August 2015, Canada will introduce a new entry requirement, known as an Electronic Travel Authorization (eTA). This will be applicable to certain international travellers who fly to Canada. Entry requirements for other methods of travel (land, sea) will not change.Starting on August 1, 2015, travellers will be able to apply for an eTA online. Citizens of united states may not require an eTA but all other visitors from countries that do not require a visa to enter Canada will be required to apply for this.
ETA is actually a new entry requirement for visa-exempt foreign nationals travelling to Canada by air.