One of the common outcries from any team in any game is when a penalty is called. Either we, as fans, lament the ref making a weak call; or we lament the player for taking the call. In the case of the latter, we bring up the importance of discipline. The value of knowing the rules and playing within them. This is because when a penalty called against a team, it usually gives a power play to the other team. Sometimes the team with the man disadvantage gets scored on to pay a price on the scoreboard for the penalty. This can decide games. Most of the time, the penalized team gets away with it without a goal against. We call this penalty killing because a success requires stopping the opportunity dead. Sometimes it's by good fortune, good goaltending, or just good positioning. However, even if it's a success, it's time spent in the game where the penalized team is down a man and cannot attack as usual. They are largely forced to defend. That's one more reason why the best kind of penalty kill isn't in limiting shots or just not giving up a goal, it's not taking a penalty to begin with. It's why reffing and discipline are issues even if the penalized kills a majority of their chances.