If I am not wrong it is like Content management system. If I make it more simpler it is like that you have hosted a website. Now the user which are registered will have their specific roles. These users based on their roles can update the information given in that website, they can add new pages on the fly means they can update any content if they are allowed to do so.
The last company I was with used Microsoft Sharepoint but only the Outlook plug-in that allowed us to make group calendars. It allowed any member of the groups to change meeting times & places @ the last minute so that we all had a good excuse for missing them since we could claim we didn't know it had been changed. The other thing it was good for is that people would post their birthdays, birth announcements, impending nupitals (shudder)& whatnot so that it was easy to find out where there was free cake that day.