Good question, i thought it was to do with the green squares that track moving objects, but even with Dynamic off i still have them so i would also like to know
Ok a little search on the interweb says
Enable dynamic analysis for motion, when Motion detection is set to ON and you have your red squares set up, anything triggering motion within the red squares will flash with green squares, basically to show you where the motion was triggered, you can also adjust the sensitivity of motion and then watch to see what lights up green
If setting up motion on an NVR a good way of working out what area is affected by movement is to cover the whole area in red squares, enable dynamic analysis, and watch to see what lights up green and what does not, you can then determine how much area is affected by adjusting the sensitivity, this would then allow you to clear which squares you do not need
if you try and do this via the web interface it does not work as it is not possible to remove individual squares.. instead you have to remember which squares to put back after clearing
