Do note that there are 2 ways to share a graphical user interface on X.
The first way is by remotely running a program on your own Xserver. The programs' processes occur on the remote connection and are sent down the SSH tunnel and show up on your display. This is the common way in Linux.
The second way is by an older program from the Windows world: VNC. VNC takes a local, running display (example: my gui) and allows someone else to view/control it at the same time I do. In this method, you both fight over the mouse and keyboard inputs.
There are several others as well. There are a couple different ways to make a "multi-head" setup in linux, which is what it sounds like. Multiple monitors/keyboards/mice all attached to the same computer allowing multiple people to run X at once independently.
The first way is by remotely running a program on your own Xserver. The programs' processes occur on the remote connection and are sent down the SSH tunnel and show up on your display. This is the common way in Linux.
The second way is by an older program from the Windows world: VNC. VNC takes a local, running display (example: my gui) and allows someone else to view/control it at the same time I do. In this method, you both fight over the mouse and keyboard inputs.