What is "MobilityState" and why does it keep appearing on my phone?

[Android Central Question]

A few times a day, I get a brief message on my phone that says either "Mobility State: UNKOWN, Mobility State: Stationary, or Mobility State: Mobile". It appears and disappears very quickly. It shows up at the bottom of the screen in one of those gray text boxes, the same type of box that appears right after you set an alarm. It happens randomly, doesn't seem to matter if I have an app open or not. Can someone please explain what this means?

 

[Tarry The Robot]

Can you please up-lode an Image of the pop up you are getting.
Br