Closing the loop means completing a cycle of actions or events. It's like finishing a big circle of things that need to be done, so you can start all over again.
Let's say you have a toy car and you want to play with it. The first step is to get the car out of the toy box. Next, you need to put batteries in it so it will work, and then you need to turn it on. Finally, you can start driving it around. Once you're done playing, you have to put the car back in the toy box and close the lid so it's safe and secure.
That's a loop, and it's been closed because you brought the toy car out, played with it, and then put it away. The next time you want to play with your toy car, you can start again by opening the toy box and taking it out.
Closing the loop is important in many areas of life, like recycling. When we put recyclable materials like paper and plastic bottles into recycling bins, they're taken to special places where they're broken down and made into new things. Once those new things are made, they can be used again and the loop is closed.
This means that we don't have to keep making new stuff all the time, which is good for the environment. It's also like completing a circle of life for those materials, because they don't end up in the landfill but instead they keep being reused over and over again.
So closing the loop is like completing a big circle or cycle of things that need to be done, and it's good for the environment because it means we're using materials in a more sustainable way.