[danabramov]

>1. Are the "Progressive Hydration" and "Selective Hydration" related to SSR? I could not find any info on what functionality is hiding behind the terms.

Yea. We'll need to expand the docs on this. Progressive Hydration means React won't block the thread while hydrating HTML. Selective Hydration means you can tell React to prioritize hydrating a particular subtree (e.g. because the user interacted with it).

>2. In general I often find it hard to navigate the API part of the React docs - for example to find the definition of a lifecycle method (for example componentDidUpdate). There is no fast way to get to a single method.

I'm not sure what this means. If I type "componentDidUpdate" in top right search bar, it jumps directly to it.