An airliner is like a big bus that flies in the sky. It has wings, engines, and a place for people to sit inside. Just like how a bus takes you from one place to another on the ground, an airliner takes you from one place to another through the air. A lot of people use airliners to go on vacation or to visit family and friends who live far away. It's a really cool way to travel because you can see the world from way up high, but you need to follow some special rules like wearing a seatbelt and listening to the pilot's instructions.