Apple Remote Desktop allows you to control remote computers as if you were sitting in front of them. You can only control the keyboard and mouse of any one computer at a time. There are two kinds of remote computers that Apple Remote Desktop can control:  Apple Remote Desktop clients and Virtual Network Computing (VNC) servers.

See:

• Controlling Apple Remote Desktop Clients
• Control Window Options
• Controlling VNC Servers
• Changing the VNC Port on an Existing Computer
• Configuring an Apple Remote Desktop Client to be Controlled by a VNC Viewer