what is a message via imessage and a message via cellular network?
iMessages are messages sent over the Internet between iOS devices. With iMessage, iPhones, Macs, iPads and iPod Touches can receive messages when they are connected to a Wi-Fi (wireless Internet) or 3G/4G network. Your iDevice will automatically send an iMessage when you message another user that uses iMessage.
To answer this question, letâs first look at a typical text message. When someone sends a text message, they type a message on their phone and hit the send button. At that point, the cellular data service provider (Verizon, AT&T, Sprint, or whoever) transfers that message through their network to the recipient.