When you first create a spline there are options to create it with or without actual "Fit Points". An advantage of having fit points while editing the spline is that you can "fix" the location of existing points while doing a re-fit. Also, while dragging a fit point with the "Drag Fit Point" option, you "fix" all other existing fit points during the drag operation. If you do not want to keep the fit points created by this function, you can use the next option to remove them before you exit this function or select a new spline to edit.