Docs for server timing

I love seeing some server timings in enhance, but I can't find any documentation about what they each mean.

Would it be possible to get some docs for what each of these are measuring:

- `enhance-api`
- `enhance-elements`
- `enhance-html`
- `enhance-preflight`

In particular `enhance-elements` and `enhance-html` as those two are the ones that take the longest (at least in my current situation).