Okay kiddo, imagine you have a chair that you sit on, and you want to turn around to talk to someone behind you. But instead of scooching your bum around and moving your feet, you have a magic power that allows you to turn your whole chair around with just a flick of your wrist. That's kind of what a swivel does.
A swivel is a special kind of joint that attaches one thing to another thing and allows it to spin or turn around while still staying attached. For example, the bottom part of a bar stool has a swivel that lets you spin around while staying put.
In some cases, a swivel can also mean a kind of hook or loop that allows something to move in different directions without getting tangled. Like those fancy phone cords that used to be popular, they had a swivel that kept the cord from getting all twisted up.
So basically, a swivel is like a magical spinning joint that helps things move around without breaking or getting tangled. Pretty cool, huh?