Just like Siri and Cortana, Facebook's new M personal assistant can complete tasks and retrieve information on the fly. But, its the way that M does it that is truly innovating over others. M receives its users commands directly through text messages, and can complete tasks such as booking flights, placing reservations, making online purchases, and more.
This is a stark difference from the voice command based digital assistants we've seen in the past. So far Facebook is has begun to slowly roll out the new app to a limited set of users. It will be available on both IOS and Android.