an accepted procedure, custom or habit.
Rules make us human, they make us civilized, they guard against anarchy. Rules make sure a prescribed pattern is set. Rules create a structure for an organization. Rules need to be abided, they guarantee results.
Rules can be unjust. You can work your way around them or let them be, ignore them.
But come what may, you must know the rules.
They need to be abided until you master them and once you have mastered rules you can break them.
You make the new rules.