This is the main interface to Virtual World Starter, it has almost the same options as the Mini version, other than the extra "Help" button that takes you to the web site (here), which you can access from the "About Box" as well in the Mini interface.
Avatar Name Server is a grouping of Avatars and Grids (which means you can use the same avatar name on a different grid, with a different password).
Grid is the grid to log in to (these will change depending on the login server above).
Software: The viewer to use.
Extra Command Line: Select whether you want to be able to launch multiple viewers (default is on), and whether you want to disable voice (default is enabled), these options will persist when you next start Virtual World Starter.
Also here you can select for this launch whether you want any other options (which are set up in "Settings" under "Extra Command Line Options", the most common are already listed).
If all you want to do is start the viewer (and not log in), then you can press "Start Only" now.
Otherwise, select the User/Avatar that you want to log in with (this will depend on the Avatar Login Server above), and press "Login".