Plugging iPhone gives IP address on a new network interface Plugging my iPhone on my MacBook Pro shows me a new network interface en7 and allocates an IP address.

$ifconfig 
en7: flags=8863&lt;UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST&gt; mtu 1500
    inet 169.254.134.xxxx netmask 0xffff0000 broadcast 169.254.255.255


Why is this and what is it for?
This is for tethering. Your iPhone can share its cellular data connection over USB (or Bluetooth) to your Mac, so your Mac can use your iPhone to connect to the internet. You can see the network interface appear in System Preferences → Network.