User @mentions enable tagging content with a user within the community. The tagged user then receives a notification that he or she has been tagged with the content. This provides a useful way to alert people that content you’ve written is something they need to review. In addition to mentioning other users of the community you can also @mention a group. When a group is @mentioned the group, and its members, receive a notification.
Tags & Hashtags
Tags and hashtags allow for creating multiple dimensions to content items. Tags can be pre-defined if desired and hashtags can be used within content similar to how hashtags are used by popular social media applications.