Emacs does not start in the background by default, so if you want to continue using your shell, you must append & to the end of your command like

$ emacs &

It is those small things that matter in life, and you might find it surprising how much stress is relieved when you don’t have to type & every time you start a crucial program. So I defined the following function in my zsh configuration.

function em() {
  (emacs "[email protected]"&)

It also works for bash. So when you want to edit a file, you can just type

$ em yourfile.txt

Note that it discards the output and error messages.