IMessage Saying Delivered Without Wi-Fi?

Okay, so I have an iPod and my friend has an iPhone without a plan, we text on iMessage, but I';m wondering when iMessage says 'delivered' does that mean they have Wi-Fi, or does it still say delivered even if they don't have Wi-Fi.

It doesn't matter if your friend has Wi-Fi or not. If he has cell service, the message will be delivered.