It is ment to be used to compare the amount of visual difference between LODs.
Select 2 objects, select if you want to compare them by rendering them out or just by taking a screenshot from the viewport and press start.
The script will show an image with red, green and blue colors wich are a representation of the amount of difference between both objects.
You can set the thresolds for these colors in the script window aswell.
Let’s say that you want all the pixels that have a difference of less than 100 to be painted in green, between 100 and 200 in blue, and over 200 to be painted in red.
What you would do is to set the Green thresold to 100 and the Blue thresold to 200.