I understand what they do mechanically. But what ARE they? They're clearly rings attached to the strike of the zaw with weird special properties. Are they some kind of powerful technology? A mystical focus? How on earth do they affect damage and crit chance? How do rings attached to a sword make it swing faster?
The game refers to them as "various weights and decorations attached to the hilt of the weapon's handle". As to how do they work? When in doubt, blame Void Magic! That's really all there is to it, you could try to stretch it and argue that the weights can influence the balance of the weapon and thus it's swing speed but then there is Status and Crit as well. The most reasonable explanation is you use various parts from the Plains, both organic and non-organic, to craft them and the Plains are known to be infused with both Sentient Energy and Kuva from the Orokin Tower. All that weird juice is causing the dangly bits you attach to the Zaws to modify them in various ways.