Closed concept

Imagine playing with a set of toys that you keep in a big box. You know what toys are in the box because you can see them and touch them. This box with its toys is called a concept.

Now, imagine that your mom comes and takes some of the toys out of the box and puts them in another room where you cannot see them anymore. The concept of toys in the box has become closed because there are some toys you know exist, but you cannot see them anymore.

Similarly, a closed concept is when you have an idea about something, but some information about it is not available to you. It means that there are parts of the idea that are hidden or not complete. This can happen for a lot of things, like a mystery story where you don't know who the culprit is until the end. The idea of the story is closed until you find out the identity of the culprit.