Bone parent = Path Constraint to Bezier Circle Then EFFECT

Yesterday I created a bone and a bezier curve. Use the CTR-P to set parent to PATH CONSTRAINT. I went into pose mode and I found something called EFFECT and I was able to control where that bone was on that path. The bone went RIGHT ON THE PATH it was not going off someplace. What did I do to make this happen where is “EFFECT” at I can not recreate this today. I know I went into pose mode. So it was this really weird way of making a bone follow a path. Now I see I can simply go into pose mode and use Path Constaint and that works. But still I wish I could understand what that other methode was about and how to find it again. It was an alternative way to make a bone follow a path by using “EFFECT” someplace in one of the settings that effect bone. What is the EFFECT for and where is that setting Can anyone elaborate ?