What does imessage mean by' circle verification'

System background automatic verification. IMessage is an instant messaging software launched by Apple, which can not only send short messages, but also send videos, address books, location information, photos and so on. Imessage keeps turning around to verify that the system automatically verifies in the background. When using the information function of Apple mobile phone, users need to activate the iMessage information function and wait for the activation verification to pass.