If you look at the hockey rink there are 5 lines, goal line, blue line, center red line, blue, goal. If you shoot the puck from your side of the red line, so that it travels all the way across the goal line before anyone touches the puck from either side the whistle is blown and the puck is brought back to your teams side
There are a few exceptions to this rule, if the puck goes in the net, even though it crossed the goal line it counts as a goal and not an icing
Another example is if you shoot it and neither team puts an effort into getting the puck, and the referee’s discretion is that someone could have touched the puck then it isnt an icing
Also if you’re on the defending teams and the puck is coming right at you and you lift your stick to let it pass that’s not an icing.
The final situation (that I’m aware of) is when you are shorthanded so you are playing with less players on the ice than your opponent
Goalies are subject to different rules, for example they can act like their going to touch the puck then decide they wont and let the puck ice
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