Using a pen or pencil, draw an arbitrary set of four points on a piece of paper, number them from 1 to 4 in any order, and then try to draw an approximation of the cubic Bézier curve defined by those four ordered control points. Then rearrange the numbering of the control points (i.e., their order, but without changing their positions) and redraw the new resulting cubic Bézier curve. There are numerous online tools for drawing Bézier curves you can use to check your approximation.