The most important g-Eclipse preference is the declaration of at least one valid Virtual Organization (in short, VO). In terms of the Grid, a VO is
[...] a group of individuals or institutions who share the computing resources of a "grid" for a common goal
Within g-Eclipse, VOs are used as the central access point to the user's personalized Grid. VOs are therefore specific for a certain grid middleware. In general, a VO implementation requires at least a contact string for contacting a specific information service. This service is later used by g-Eclipse to query the Grid - or, to be more precise, the underlying middleware - for available resources such as computing elements, storage elements and other services.
Subsequent chapters describe tasks, which you may do to manage VOs in g-Eclipse.