Unicom's mobile phone card sent a text message saying that it has accepted domestic data roaming service? What kind of business is this? Is it the one with a flow of 5 yuan and 30 meters?

This is a data roaming service for Unicom users, but the donated data traffic can be used nationwide (except Hong Kong, Macao and Taiwan). This is business, not specific traffic. Only by opening this service can the traffic you send be enjoyed in different places.