As the booking reference, the eTicket is a document that helps us to identify the passenger and then to make a claim on his behalf.
The eTicket number is a 13-digit number that uniquely identifies the airline ticket that was issued to you. You can locate your ticket number with:
-the boarding pass: which is issued to you at the time of check-in.
-the eTicket receipt: Which is issued to you by e-mail at the time flight reservation is made.
If you received an eTicket via e-mail, the booking reference is the six character alphanumeric code that appears to the right of the booking reference field.