Motivation:

You want to sync content between your MacBook and iPhone over Wi-Fi.

Solution:

1. Connect your iPhone to your MacBook using a USB or USB-C cable.
2. In the Finder on your MacBook, select iPhone in the Finder sidebar.
3. Click General tab in the button bar.
4. Select the Show this iPhone when on Wi-Fi checkbox.
5. Click Sync button.
6. Unplug your iPhone from your MacBook.
7. Restart both devices.
8. From now on, when your iPhone and MacBook connect to the same Wi-Fi you will see your iPhone device in the Finder sidebar, and you can sync content between them without having to use a cable.
9. Sometimes if your MacBook cannot find your iPhone then just restart your MacBook and it will find your iPhone device again.