What would a chat bot do in a chat app? Now butt in hopefully. But Cortana could, at your command, chat for you if needed. Of course, it won't be holding a conversation with your friend but will instead suggest things to answer back. And if you need to, you can even talk to Cortana directly. That is what Cortana is bringing to Skype users on Android and iOS, bringing the battle of AI assistants to your messaging.