I don't think componentDidRender is a substitute for componentDidMount because the component can render multiple times when props change after it's mounted once.

so mount can be called "placed"?

Ignoring React you can think of these two native functions as mounting: replaceChild appendChild Which are likely the most common functions React uses to mount internally.

Mounting refers to the component in React (created DOM nodes) being attached to some part of the document. That's it!

And, yes, Mounting is also an unfortunate/confusing name, if you ask me. IMHO componentDidRender and componentWillRender would be much better names.

This process of creating instances and DOM nodes corresponding to React components, and inserting them into the DOM, is called mounting.