KLO

I have seen these attachments advertised but don't really know anything about them. Does anyone use this device and where/why would you? Is it like a serger in that the fabric is cut away from your stitching as you sew? I am trying to figure out if this is something worth buying. Thanks to anyone in the know who can elaborate on this item.

edited: Why did I not think to check youtube? I am in the process of seeing how to use this foot there. Still, I wonder how many of you use this and for what kind of projects? And is there a difference between this and I think what is called a "side cutter foot" that looks different that this attachment.