They operate on the basis that when you tie one to a wrist or ankle, you wish for something as you tighten the knot. They are made of natural materials- a cord and some beads, perhaps- and the cord is meant to deteriorate with wear and time. When this eventually happens, either the entire bracelet will fall off, or just the beads. This means that your wish has been/ will soon be granted.
I enjoy making them; they are simple and in that lies the beauty. I am used to planning where each bead and knot will go before I make anything, but with this you just braid until you decide to add beads, then braid some more until you think it’s long enough. I think I may sell them. One or two dollars perhaps.