Picture shows broadcast requests of the devices and their IP addresses needed to establish communication on the network. Not shown is also ARP reply, where and assignment of IP to MAC happens.
Since IP addresses can change, why can't devices (mobile phones, routers, laptops, tablets) then just use MAC addresses instead of IP to communicate with each other, to skip the whole Internet Protocol thing and why spoof ARP?
The simple answer to this is: why cant postmen deliver packages addressed to: eg. “Joe Doe”?. Well first of all, postmen don’t know where Joe Doe is located in the first place. What if you change your home address or town, how will they know where to deliver your package ? In networking terms, MAC is your name, external IP is your home address; internal/private IP is your device address you used to initiate communication from.