Does ANYONE understand them? Depressingly it seems not.
If you're joining us late, many years ago there existed a thing oft bemoaned by fans and pundits alike, called the "professional foul". This was a cynical deliberate foul, typically committed by a lumbering centre-half when he'd been skinned by a forward who was then heading clean through on the goalkeeper, but still a long way from goal. The centre-half would blatantly haul him down, making no pretence at a legal attempt to win the ball, and give away a harmless free kick perhaps 30 or 40 yards out.
The forward would thus be denied a chance to go one-on-one with the keeper and very likely score. The defender, meanwhile, would suffer only a yellow card at most – because his foul was in itself usually innocuous (being a simple trip or shove), leaving the referee no grounds on which to issue a red. It was clearly unfair, and something had to be done.