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It's for getting notifications, not for following people. So you enter your account name, and you'll get notified when ever someone votes/replies/resteem your post, or if someone follows or mentions you. But it will only get notifications while ever your browser is open. It won't notify you for any activity that happened while your browser was closed. I'm thinking about adding a service where it stores all your notifications whether you had your browser open or not. Would charge probably 1SBD/STEEM per month for that, as the database size and server process size will grow significantly with that feature.