What's the difference between hydrate() and render() in React 16?

Question

I\'ve read the documentation, but I didn\'t really understand the difference between hydrate() and render() in React 16.

I know hydrate()

Answer 1

render will flush out anything in the specified element(named as 'root' in most cases) and rebuild it ,while hydrate will keep anything that is already inside the specified element and build from that,making the initial page load faster.