Earlier quoted context omitted.
Emacs users should be using Emacs as their terminal multiplexer...
One reason to run Emacs in tmux is if you work on remote machines over, e.g. ssh. Emacs in tmux (or screen) lets you detach, log out then log back in and re-attach to the remote session with Emacs still running. That's amazingly handy.
C-h f server-start