 So sometimes you just feel like collapsing, not a problem. If you left click an edge it will collapse the point closest to your mouse to the next point. If you hold left click you'll be able to switch the direction back and forth. Polyloop does the exact same thing, but instead of collapsing to a single point on the edge it merges the entire edge loop. And Hole will merge an empty loop into a single point. Hope that helps and as always I hope you have a fantastic day and I'll see you around.