The tire swing is commonly used by a lot of characters. What themes or ideas does the swing convey through this?

After settling in at "Out-With," Bruno gradually starts to explore his new surroundings, but with no one to play with, he finds himself bored most of the time. To make the time pass more easily, he builds himself a tire swing. He gets the spare tire from Lieutenant Kotler, grabs some rope from the garage, ties them together, and hangs them from a large tree.
At first, the tire swing is an agreeable way for Bruno to fight off boredom, but the fun doesn't last very long because he soon falls off the swing and scrapes his knee. Bruno's family's Jewish servant, Pavel, comes to the young boy's assistance. It is while he's tending to Bruno's injuries that Pavel reveals that he used to be a doctor. For the first time, Bruno is able to see Pavel not as a servant to be barked at and physically abused but rather as a human being.
In that sense, the tire swing could be said to symbolize freedom—not just the kind of personal freedom you enjoy when you go off and do your own thing, but the freedom to think for yourself, and that's something that Bruno's never been allowed to do before. Like many German children under the Nazi regime, he's been indoctrinated from an early age to believe that the Germans are the master-race, but his brief encounter with Pavel after falling off the swing has given Bruno food for thought and made him start to think that maybe the warped Nazi worldview that he's been taught isn't true after all.