Talking via Messages and FaceTime
macOS comes with the Messages application, which you use to exchange instant messages with other macOS users, as well as anyone with an iPhone, iPad, or iPod touch. You can use FaceTime to make video calls.
Sign In to Messages
Your Mac includes the Messages application to enable you to use the iMessage technology to exchange instant messages with other people who are online. The first time you open Messages, you might be required to sign in with your Apple ID. Note that signing in is optional. ...