The difference between Apple SMS reading and delivery.

1 and "sent" indicate that the SMS has been successfully sent to the other party's mobile phone, but the other party has not opened the SMS or the mobile phone is in a state of being unable to receive SMS, such as power off and airplane mode.

2. "Read" means that the other party has opened the short message and read its contents. By default, the "read" status of Apple SMS can only be displayed if the other party has turned on the "read receipt" function. If the other party does not turn on the "read receipt" function, then even if the other party has read the short message, the sender cannot know whether the short message has been read.