What is the red 'walking man' icon?

I've looked through the Reolink Client manual, but cannot find anything showing what the red 'walking man' icon means in the upper left that appears at times. Anyone know?

That is the "Motion" detected icon. If you have motion recording enabled, the camera will be recording when that icon is showing. When you do not see the red man icon, it means the camera has not detected any movement or motion.

You can have a look on Page 24 of the Reolink Camera Client - User Manual covering Alarm -> Motion events. It is located in the "User Manual Cam" zip file on the site here: https://reolink.com/software-and-manual/