2. Characteristics of each stage: The first stage is traditional services, with a two-level system of central bank and commercial banks. Most transactions are made by cash and passbook; In the second stage, UnionPay clearing center appears, and different banks can carry out clearing. The third stage is that after the emergence of electronic payment and online payment, many third-party payment platforms have appeared outside UnionPay, which is a very effective supplement to the traditional financial system.