From Online Manual
When a user sets up an SMF forum, or wishes to join another SMF forum, they should register an account. This will enable them to maintain a consistent identity while posting and keep track of what they have read, no matter where they are working from or what computer they are using. They will be able to fill out a personal Profile and use the built-in Personal Message system. They will also be able to subscribe to e-mail notifications, monitor their forum activity and more.