 So, you don't understand behind and polygroups, not a problem. This is exactly the same thing as behind, except instead of applying the actions to everything that is behind the face you start with, it only applies actions to things behind the face you start with that are also the same color as the polygroup you start with. So here you can see I'm clicking on a pink polygroup, so only the stuff behind that is also a pink polygroup is going to be affected. That's all it means. Same thing with the addition of a polygroup color filter. So same thing if we have a green polygroup here and here and here and target is set to behind and polygroup. If we left click here, even though all these are the same color green polygroup, it only applies the action to the ones that are also behind. So that's how that works. Hope that helps and as always up you have a fantastic day and I'll see you around.