log into iMessages

iPads, even iPads with cellular capabilities, are not able to receive or send SMS or MMS natively, as these services travel on your cellular provider's voice network. Signing in to iMessage gives you two chances at working around this limitation.

First, iMessage will give you access to Apple's iMessage/FaceTime service. When registered, you will be able to communicate with any other Apple device user via WiFi or Cellular Data, wherever you may be. Further, you will also be tethered to your iPhone that uses your same Apple ID whenever the two devices are near each other. This will allow your iPad to use your iPhone's SMS/MMS capabilities to exchange messages with non-Apple users, such as Android cell phones and select VoIP service subscribers.

Of course, if you intend never to use messaging or FaceTime communications on your iPad, you can choose not to engage iMessage.