Add FAQ (#1883)

docs/index.rst

@@ -14,6 +14,7 @@ Table of Contents
    using/specifics
    using/recipes
    using/troubleshooting
+   using/faq
 
 .. toctree::
    :maxdepth: 2

docs/using/faq.md

@@ -0,0 +1,17 @@
+# Frequently Asked Questions (FAQ)
+
+## Why we do not add your favorite package
+
+We have lots of users with different packages they want to use.
+Adding them all is impossible, so we have several images to choose from.
+[Choose the one](selecting.md), that is closest to your need and feel free to [add them on top of our images](recipes.md#using-mamba-install-or-pip-install-in-a-child-docker-image).
+
+## Who is jovyan
+
+Jovyan is often a special term used to describe members of the Jupyter community.
+It is also used as the user ID in the Jupyter Docker stacks or referenced in conversations.
+You can find more information [here](https://docs.jupyter.org/en/latest/community/content-community.html#what-is-a-jovyan).
+
+## How to give root permissions to the user
+
+We have a [recipe for enabling root permissions](recipes.md#using-sudo-within-a-container).