Each file represents a configuration root object, such as `params.toml` for `[Params]` , `menu(s).toml` for `[Menu]` , `languages.toml` for `[Languages]` etc…
By etc. does it mean there are other undocumented formats?
No. —
I thought to define an authors.toml for a blog I run with a couple of friends, but I will default to params.toml (maybe that etc. should be removed from the docs).
Yes (not “formats”, but top level objects in config) 
Example: Configure Hugo | Hugo
No, there are many config sections which are covered by the “etc”, but they are documented.
That’s outside my knowledge for now.
Makes sense. It confused me as I though there are othe toml formats undocumented.