Okay kiddo, a liftback is like a big door that opens at the back of a car instead of the sides like normal doors. It's kind of like a secret door that you can use to put things in the car.
When you push a button or lift a handle, the liftback door swings up and opens, and you can put things like groceries, toys, or suitcases inside. Then you close the liftback and go on your way.
Sometimes people with liftbacks can even put bigger things in the car like furniture or even bikes! It's a really cool feature that makes it easier to get stuff in and out of the car.