Imagine you're playing with your toys and you have a big toy box. You know how sometimes you need a smaller box to keep your smaller toys in? That's kind of like what an auxiliary unit is. It's a smaller thing that helps the bigger thing work better.
Now, let's think about a car. A car has a big engine that helps it go fast and has wheels to help it move. But there are also smaller things in the car, like the radio or the air conditioning. Those smaller things are like auxiliary units because they help make the car more comfortable or enjoyable to use.
In factories and buildings, there are also big machines or equipment that help get things done. But sometimes those big things need smaller things to help them work better or stay safe. For example, if you have a big machine that makes metal parts, you might need a smaller auxiliary unit that cools down the metal quickly so it doesn't get too hot and break.
Overall, an auxiliary unit is just a smaller thing that helps a bigger thing work better or safer. It's like a little helper for the big thing!