Why can Apple send and receive text messages at the same time?

After setting up, both phones can receive it. The method is as follows:

Open imessage in the settings and you will receive it;

Two Apple phones use the same ID. If it is not set, two SMS messages cannot be received. If there is imessage in the settings, it will be accepted by two Apple phones at the same time. The premise is that if there is a network, it is imessage.

You can check whether iCloud is enabled. Two people use the same ID. If iCloud is enabled, they will receive each other's information and other materials, and the download will be synchronized. You don't need this function to set where to close. When turned on, the functions will be relatively synchronized, just like the functions of mobile phones and network disks.