Illegally interfering with a clear goal scoring opportunity by a defensive player, such as by grabbing the shooting arm of the offensive player from the side or from behind, will result in a penalty shot. Much like in soccer, the shooter is “expected” to score.  Another common occurrence is playing defense inside the 6 meters line.  This often takes place when a defender slides over to help.  As the defender tries to get in front of the advancing offensive player the defender loses track of the line and ends up defending inside the 6 meter line.