How does Apple SMS trigger special effects for the second time?

The method of sending special effect SMS by iPhone can be realized in the following two steps:

1. First open Settings-Info to find the option for iMessage and make sure it is turned on. If you do not open it manually, you will be prompted to send an activation message. 2. After opening, if the other party is not an iMessage user, the information sent is green, and the information of iMessage user is blue. The green ones use SMS numbers, and the blue ones surf the Internet for free. You can also reply to iMessage with a tag, such as likes and questions.