ELI5: Explain Like I'm 5

Conjugacy-closed subgroup

Okay, imagine a group of toys playing together. Each toy has a special power, and they can form groups based on the way they use their powers.

Now, let's focus on a special type of group called a conjugacy-closed subgroup. This means that this group has a very interesting property.

When the toys form a group, they can do a special trick called conjugation. This trick involves moving their special powers around in a special way. It's like shuffling the special powers between the toys.

In a conjugacy-closed subgroup, whenever you take two toys who are already in the group and you do this special trick of conjugation, the result is another toy that is also in the group.

Let's use an example to understand this better. Imagine the toys are numbers, and their special powers are the ability to make other numbers bigger or smaller. And let's say we have a group that consists of the numbers 1, 2, and 3.

If we take the number 1 and the number 2, and we do the conjugation trick, the result is the number 2 and the number 1. And guess what, both of these numbers are already in our group of 1, 2, and 3. So this means our group is conjugacy-closed!

Now let's try another example. Imagine our group consists of the numbers 1, 2, and 4. If we take the number 1 and the number 4, and we do the conjugation trick, the result is the number 4 and the number 1. Now, in this case, the number 4 is not already in our group of 1, 2, and 4. So this means our group is not conjugacy-closed!

In conclusion, a conjugacy-closed subgroup is a special type of group where if you do the conjugation trick with two toys in the group, the result is always another toy that is also in the group.