What's the difference between text messaging and iMessages? Text messaging requires that you have a cellular plan while iMessages allow you to send messages using your cellular data or Wi-Fi. This is especially handy if you're travelling internationally with only a Wi-Fi connection, or if you want to send messages from an Apple device without cellular connectivity. If the message you send is blue, it's an iMessage; if green, it's a text message. Here's how to set iMessages up if you haven't already.