Croquet can be the girl next door or the prom queen. She's flexible like that. But she draws the line in certain places. Sometimes. Depending on what kind of mood she's in.
In croquet, a fault is a rule violation. If you accidently kick an opponent's ball, for example, that can be a non-striking fault. If any part of your mallet besides the end-face makes contact with the ball during gameplay, that's a striking fault. Depending on the rules you're using, different faults have different consequences and remedies. Sometimes players lose turns and points, but sometimes play simply resumes. In certain situations, balls are left as-is despite the mix-up, and in others they go back to their original positions at the discretion of the non-faulty party.
Depending on the rule set, if you send an opponent's ball through a hoop, your opponent may earn a point. In other versions of the game, you can earn extra whacks at your ball during your turn. For example, running a hoop could get you an extra shot. If you run the hoop and send an opponent's ball through it too – the other ball has peeled the hoop if this occurs – you may still earn a point but not get an extra stroke. But note: You can't generally save your shots for later. You take them when you earn them ... except in some situations, such as when you're playing with handicaps.
There's also the croquet/roquet method. If you hit another player's ball (called making a roquet) during your turn, you can put your ball right next to the roqueted ball. Then, holding your ball still with your foot, you can hit it and watch your opponent's go spinning away on the other side (aka taking croquet). It's physics in action (thanks, conservation of energy and momentum!) and it can give you a serious strategic advantage.
And don't get too far ahead after running a hoop – under some rule sets, your opponents may call offsides on the play. In some instances, players who go past the halfway point between one wicket and the next have to take a penalty shot.
A few variations are more about the field than how the game as played. Players can use markers to help keep track of things during the game. For example, corner flags in the four colors can assist competitors with directional guidance or simply spruce up the court. You can also place pretty clips on the wickets to help you remember which balls have run that hoop.