Rules are strict and rigid. They remain stagnant, and are set to accomplish only one thing, like 1) Do not touch, 2) No soliciting, 3) You must subscribe to this blog.
Rules are boring, and you are meant to follow them, even though they have only one option. And when you break the rule, everyone goes bat [insert swear word] crazy.
Systems are different. Systems provide options.
In basketball, you learn different systems for offence and defence. There are several options in your offensive set up, generally with the first 2 options meant to go through your best players. But there are also options to go into the post, or set up an open shot for that player who isn’t the best all-around player, but a damn good shooter. In defence, if you get beat by the person you are defending, the team system allows for “help defence”, wherein a teammate leaves their man to help guard yours. Systems provide different options when your initial play or intended outcome doesn’t work.
Systems are more like guidelines that flow, rather than rigid rules. At any moment, you can break the system, easily, and go your own path if you see fit. This is generally what [used to] happen when Kobe Bryant has the ball and decides to absolutely destroy his defender by himself.
Create systems, don’t follow rules.