Liquid dielectric is like a special kind of liquid that's used to help keep electricity from going where it shouldn't. You know how you shouldn't touch electrical sockets or wires because it can hurt you? Well, liquid dielectric helps to make sure that the electricity stays inside the wires and doesn't shock you or start a fire.
It's kind of like putting a fence around cows so they stay in the field and don't wander into the road. The liquid dielectric is like a fence that keeps the electricity in the wires so it doesn't go where it shouldn't.
Some people use liquid dielectric in big machines or power grids because it helps to make sure that the electricity flows smoothly without causing problems. So just like how you need to follow the rules and stay safe around electricity, machines need liquid dielectric to keep everything running safely and smoothly.