Prime Minister Narendra Modi on Friday launched an Aadhaar-based mobile payment application at 'DigiDhan Mela' here to promote and make digital transactions easier. The app is called BHIM (Bharat Interface for Money) -- a re-branded version of UPI (Unified Payment Interface) and USSD (Unstructured Supplementary Service Data). Speaking on the occasion, Modi said BHIM app was very simple to use and a thumb impression was enough to operate it.