Real life scenario: you have a headless server that has GUI software installed at a remote site. You connect to the network from home with a VPN. Then SSH in to the server with "ssh -X user@server" and run the GUI program in that terminal. The GUI appears on your local display. SSH sends the X11 protocol traffic through an encrypted tunnel from the remote server to the local X11 display server, because of the -X.
Real life scenario: you have a headless server that has GUI software installed at a remote site. You connect to the network from home with a VPN. Then SSH in to the server with "ssh -X user@server" and run the GUI program in that terminal. The GUI appears on your local display. SSH sends the X11 protocol traffic through an encrypted tunnel from the remote server to the local X11 display server, because of the -X.