Tap the Running Man icon to turn Motion Detection on or off for that camera.

A solid blue icon means the camera is actively watching for motion.
A lighter grey icon means the camera has motion detection turned off.

By Arming your system, and then selecting certain cameras, you get motion clips just from the areas you are interested in. For instance, you may want to be alerted to visitors at the Front Door, but not your dog running through the Garage. In this case your Home screen for the system will be similar to the image below.

The Running Man is active  for the Front Door camera, and inactive for the Garage, even though the Home Front system is "Armed".

The Running Man remembers how you set it, so each time you Arm your system, the results are the same.

What if I want to change Motion Detection without Arming my system?

When your system is Disarmed, the Running Man is not visible. You can "Enable" Motion Detection from the device Settings screen when you tap it's settings icon   on the Home screen. Click to learn more about how to adjust camera settings‍.