Documentation
The documentation contains information about the platform/plugin/mods, specifically their functions, instructions, and for plugins commands, permissions, or placeholders, etc. You can almost always find a link to it on the project page from where you download the plugin/platform.
If you don’t know your way around a particular setting, the documentation is where you should look first.
As with configuration files, you can search in browser in text (keywords), which can make searching easier. Just use the Ctrl + F shortcut to enable text search. The documentation page often provides search function too.