If we slapped a bunch of sensors on Mary, we may know things like her current location, current body temperature, her heart rate, her blood pressure. If this information is communicated to your model in real time, you have an active, living representation of Mary that tells you more about her than she may know herself.
Imagine applying this same process to your house, your car, your toaster, or your favorite pair of socks. Now, maybe you can’t think of a good reason for your socks to talk to your toaster, but they may have a thing or two to share with your washing machine.