A discussion board on LinkedIn for people of like interests to share user-generated comments, news, images, and other content about a specific topic.  Groups have an owner and moderators, who may remove or promote specific content.

LinkedIn Groups allow you to interact with like-minded professionals and share ideas. A LinkedIn Group is set up in a forum style format. Participation on a regular basis will grow your personal brand presence and establish you as a subject matter expert. LinkedIn has considerable more information on the groups functionality and the types of groups that are possible. Here are extensive LinkedIn Tips on LinkedIn Groups.