How do I create a tree system? Before I knew Drupal, I made a CMS that was working like Wikipedia, where each page and link could have parent and children. Now I want to create that website with Drupal.

Is there any module for this?

This is what I need: Each page may have children, and each children may have children too and so on.
There is a core module namely 'Book' . Use that module to get desired structure of pages.

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