The e-ticket is a record in the booking system of an airline that contains all the information about the flight, passenger, and payment, whilst the boarding pass documents is a document (either paper or electronic) that shows a gate agent that you’re allowed to board a plane for a particular flight.
For more information regarding check-in, please go to your airline's official website. You'll find some other flight-related-information on its online pages that may be quite useful for a successful journey.
We urge you to repeatedly check the airline's online resources, once in the process of booking, then a few days before the departure, to make sure nothing has been missed.
(Note: If the carrier does not support online check-in, please be sure to present your e-ticket to the airline service counter to be granted a boarding pass.) Additionally, we counsel you to contact the carrier 72 hours prior to the flight and go through the itinerary together as well as confirm it, to avoid last-minute amendments.