The session dialog is divided into two sections: bookmarks and command parameters
Bookmarks are predefined commands, either from a system administrator (Global), or from the user (User). Clicking on a bookmark fills in the command parameters. From there a user can edit the command as needed.
A command is required to start a new session (e.g. xterm, gnome-session, virtuoso). This will be the command that is first launched. The session runs until the command exits.
The Window Mode defines the type of session to run. Multiple Window Mode means all windows are separate and act as if they are part of the client OS itself. Single Window Mode contains all windows in one single window. A remote Window Manager is needed to move windows around