Parent Attribute in Parent-child hierarchy

Dear Experts,

I am trying to do a deep dive into Parent-child heirarchy construct, and had been trying to figure out the concept of Parent attribute.. I know that Parent attribute has been described in various replies in the forum as below:

'A parent attribute describes a self-referencing relationship, or self-join, within the main table. Parent-child hierarchies are constructed from a single parent attribute'.

I would appreciate if someone can clarify this concept a bit with an example.

regards,

Pooja