Facebook Groups
There are a lot of groups on facebook and they can be very effective in creating exposure for a businesses or products. Anyone with a facebook profile account can create a group. It is not recommended to only use groups for a business. In my opinion, every business should have an official Facebook Page. Groups can be setup to enhance the marketing of the business.
Groups are made up of members, not friends or likes. You can ask to join a group which may or may not be approved. Some groups are private and only available to members that are added by other members. Group moderators will typically post rules for the group and they ultimately control "who is in" and "who is out"
The moderator can also choose to delete your posts and comments if they feel they do not follow the rules of the group. Be careful when joining someone else's group that may not allow posting or solicitation to other groups or pages.
Example of Group Use:
In my example of James Smith's Bar called Jim Bob's Bar, James may set-up a group called "Friends of Jim Bob" or "Panther Fans at Jim Bob's Bar" or "Football Club at Jim Bob's Bar" to create things in common at Jim Bob's Bar. He may choose to moderate the group or ask a employee or marketing agency rep to moderate the group.
The group may want to feature special events or provide ways for customers to interact outside of the official page. A customer may be willing to share their pictures with a select group of people in a moderated group of people they know rather than the official page where a lot of people they do not know can see them.
Group Chat Rooms
Admins and Monderators may elect to provide rooms for sepcial topics. These could be invite only or open to anyone in the group