Remote Access is made possible with Vino, a VNC server which displays the current session. You can enable other people to connect to your computer by going to System-->Preferences-->Remote Desktop and enabling the options you desire there. If you are behind a router you must configure port forwarding for remote access to work.
The following tips are taken from http://www.bani.com.br/index.php/2007/04/25/hidden-features-of-vino-remote-desktop-access/
You can edit advanced settings using the gconf-editor program. The keys to edit are located at /desktop/gnome/remote_access
- You can change the port (default is 5900), by setting the keys use_alternative_port and alternative_port;
- You can reject connections from the network and allow only those from localhost (useful for who wish to exclusively use a tunneling mechanism to access the server, such as ssh), by setting the key local_only.