What does it mean when it says the phone number is not registered with iMessage?

[iMore Question]

What does it mean when it says the phone number is not registered with iMessage

Can't sms on my iPad

 

[kch50428]

Re: What does it mean when it says the phone number is not registered with iMessage

Is this a cellular iPad? You'd need to set up iMessage to use the iPad's cell number in order to have iMessage use it as a send from/to address.