The ability to make and receive phone calls over a wireless internet connection on Apple mobile devices allows users to bypass cellular networks when a Wi-Fi network is available. For example, if a user has weak cellular coverage in their home but a strong Wi-Fi signal, this feature allows them to place calls using the Wi-Fi network instead of the cellular network.
This functionality is significant because it enhances call reliability in areas with poor cellular reception and can potentially reduce cellular data usage, especially during international travel where cellular roaming charges may be high. Originally introduced to address coverage gaps, it has become a standard feature, improving the overall communication experience for users.