X11 forwarding is method of allowing a user to start a graphical applications installed on a remote Linux system and forward that application windows (screen) to the local system. The remote system need not to have X server or graphical desktop environment.

What does X11 forwarding do?

X11 forwarding is a mechanism that allows a user to start up remote applications but forward the application display to your local Windows machine.

What is X11 in Linux?

The X Window System (also known as X11, or simply X) is a client/server windowing system for bitmap displays. It is implemented on most UNIX-like operating systems and has been ported to many other systems.