This is new. To prevent identity confusion, Twitter is experimenting (beta testing) with a ‘Verified Account’ feature. They are working to establish authenticity with people who deal with impersonation or identity confusion on a regular basis. Accounts with a 
are the real thing!
Twitter is currently testing verification with some businesses and working hard at making this feature available to all businesses. While they are not accepting new business verification requests, if you have already submitted one, they have you on our list.