Setup raspberry pi vnc server (X11VNC)

Typically, a VNC server is installed on Raspberry Pi to remotely control the desktop. By VNC client you get a virtual desktop of  Raspberry Pi on your own computer. With this remote desktop you can then remotely control Raspberry Pi or remotely control it.
VNC is especially useful if you prefer to work with a graphical desktop instead of using SSH on the console or if you want to peer over someone’s shoulder and provide remote support. The advantage is that screen content can be mirrored.