What does the exclamation point in Apple 14 mean?

Apple 14 message has an exclamation point, but the message is not opened. The specific operation process is as follows:

Tools/materials: iphone 14, iOS 15.4, information.

1, starting with an exclamation point.

2. Click the Settings icon on the desktop.

3. Open the phone settings interface and click the information option.

4. Open the information interface and click the switch button in the imessage information bar.

5. At this point, the imessage information bar is light green after it is successfully opened.

6. When you exit the desktop, you can see that the exclamation point on Apple's SMS has been deleted.