A group has some fairly common data elements.  A few of which include: Name, Description, Address, and Web Site.  A group is also an easy way to associate multiple users with a common interest or entity.  Within Active Social, a group also has numerous features which have unique permissions to that specific group and members of the group.  Depending on how much customization you would like to do, you can even have unique templates and designs for each group.  

Tomorrow we will be releasing another update for Active Social which includes a new feature called "Group Types".   A group type allows you to further define the actual purpose of a group.  For example, let's say you are using Active Social for the community section of the website of a Software Company.  The obvious choice for implementing groups would be for each product and members are those that have purchased or might be interested in the product.  Another purpose for a group could be to associate customers from the same company.  You could create a group type called Company.  You could setup one master contact for the company (group owner) which could manage who belongs to that company.  Within the "Company" view you could create custom tabs for creating help desk tickets, downloading updates, viewing license information, etc.  You could use the Active Social API to automatically create the "Company" after a product was purchased and then populate it with all the relevant information from the purchase.  

The scenario above is just one example of extending groups for multiple purposes.  If plan your site properly using Categories and Group Types, you can use groups for many things including: Directories, Catalogs, Property Listings, Project Management, etc.  Hopefully this will give you an idea of the flexibility within Active Social.