Modules populate dynamic information that links throughout the site and relates to the appropriate pages. Many modules have subscription options for your customers that allows them to subscribe to updates to the calendar, agendas, etc.
Information in Modules is generally brief and responsive to specific customer needs. This allows modules to be very specific: events for the calendar, alerts for the Alert Center, agendas in the Agenda Center, and so on.
Modules generally organize by category. Often administrative users are given access to specific categories that fit their role; permissions support this structure.