Activated Carbon
Activated carbon is a form of charcoal with tiny holes that trap dirt and toxins from water or air.
Think of it this way
A kitchen sponge soaks up spills because it is full of tiny holes. Activated carbon works the same way. The carbon is packed with holes too small to see. Dirty water flows through, and the holes trap the bad stuff inside.
Explaining activated carbon by grade level
Think of a sponge with very tiny holes. When dirty water goes through it, the bad stuff sticks to the holes. The clean water comes out the other side. The more sponge you use, the more bad stuff it can grab.