M-! : shell-command, execute entered command and insert output in minibuffer.C-u M-! : execute command and insert output at point.M-|: shell-command-on-region, executes command using region as input.C-u M-|: same, but replaces region with output from command.
Example:
C-u M-| uniq
A shell session can be started with M-x shell
EShell is the Emacs shell