I didn't remember how to achieve that and i'm stuck.
I've got a site say www.example.com and the other folder www.example.com/paperwork/ I would like when someone visits the www.example.com/ he'll be rerouted privately to www.example.com/paperwork/ but nonetheless see within the URL www.example.com

And even when the consumer types www.example.com/paperwork/ I would like him to determine www.example.com within the url
This is the user won't realize that there's a paperwork folder.

Simultaneously I would like a person who visits a.example.com and b.example.com can click on them quickly and easily and will also be motivated to go in a account information.
Any help ?

Try these rules:

RewriteCond %{THE_REQUEST} ^[A-Z]+\ /docs/
RewriteRule ^docs/(.*) /$1 [L,R=301]
RewriteRule !^docs/ docs%{REQUEST_URI}