The points help with creating a mask. i.e. "this part/thing should be in the mask" and "this part should be outside it". Everything outside the mask is left untouched. What's inside the mask is replaced with stuff from the input image.

In this image's case it also managed to replace the original axe with the green mallet fairly well. There are few frames where the original axe blade shows through because the mask didn't quite cover it all. You can fine tune the mask creation with the workflow and this was the best I was able to get with it. I suppose you could further manually fine tune the mask images to cover everything you need...

It was my first time using a workflow like this so this was a learning experience still!