When should you use mounted in simple terms?

Question

Vue.js

Read to dock, did not understand when exactly it is necessary to use it.
Also what is "mounted" in this article :
created - the component instance is created
mounted - the component instance is mounted( How to understand mounted? )
updated - the virtual DOM has been updated due to a data change
destroyed - the component instance has been destroyed

Answer 1

Included in the DOM tree