1. Default number: The main number will be used as the default number for voice, SMS, data, iMessage information and FaceTime calls, while the travel number can only be used for voice and SMS.
2. Number label: In the system settings of Apple mobile phone, both the main number and the travel number can be set as different number labels, such as "business", "travel", "personal" and "data flow", and can also be customized.
Generally speaking, the main difference between Apple's mobile phone main number and travel number is the default number and number label.