An eTA is an Electronic Travel Authorization issued by The Government of Canada.
The confirmation is usually received a few minutes after the request is processed however, some requests may take longer to be approved.
The request and approval are linked to your passport. You will need to travel with the passport you used to apply for your eTA. Once approved, an eTA is valid for multiple entries for up to five years or until the passport expires, for guests arriving by air only.
For further information on eTA's please visit the dedicated website:  http://www.cic.gc.ca/english/visit/apply-how.asp