Connecting to a remote computer is very powerful, because you can access remote files, remote applications, and so forth. Those of us building home automation or other Internet of Things devices sometimes install those devices at a remote location behind a NAT firewall, and then need to access the computer's desktop environment. For example, I have a Beaglebone Black at a remote site over 3000 miles away, and needed to run Firefox on the BBB to access some things. It's not feasible to go to the device in person, therefore the question is how to access the remote desktop.
VNC is the primary choice for this purpose. It has a lower bandwidth requirement than running X11 over the Internet, plus you avoid the complexity of installing an X11 server on Windows or Mac. Simply install a VNC client, instead. The key hurdle is getting past the NAT router.