Mailman 3 documentation
Mailman 3 is still pretty new, and most of the docs are built with the packages: Links to all the docs
Unlike Mailman 2, Mailman 3 has been divided into a number of parts:
Mailman Suite refers to the collection of related Mailman projects that provide all the pieces of a typical mailing list management setup.
Mailman Core is the part that delivers the emails and handles the mailing list and user data
Postorius is the web interface that allows users (list members, list admins, moderators) to change their user settings and the settings for their lists.
HyperKitty is the archiver which provides a web interface to access GNU Mailman v3 archives as well as ways interact with the lists. It can behave a little like a web forum, for those who prefer not to use email.
MailmanClient is the library that provides official Python bindings for the GNU Mailman 3 REST API. This allows you to write your own front end or scripts for interacting with Mailman. (It's also what Postorius uses to interact with Mailman Core.)
Mailman Bundler is a tool to help you install all of Mailman Suite via PyPI
A typical install would use all of these pieces together, but they're intended to be modular so you could replace a single piece if you had specific needs.
How do I install Mailman 3?
Right now, the easiest way is probably to use the Mailman 3 bundler.
The http://mailman-bundler.readthedocs.org is reasonably comprehensive. It guides you through an initial setup and then gives tips on how to switch it to a production setup. The production documentation hasn't been tested by a huge number of people yet: if you have any suggestions on how it could be improved, please file documentation bugs on GitLab or let us know via the mailman mailing lists.
How do I install Mailman 3 directly from git?