Ice hockey is team sports, that was invented in Canada. In modern ice hockey there are four lines witch all have five players and team have goalies. It is played in a ice rink so in game, there is 12 players in the rink at same time. Mainly the rules of ice hockey are maid by International Ice Hockey Federation (IIHF) AND National Hockey League (NHL). They have rules about the size of the rink, safety equipments, what tie-break methods they use and they make rules what players can and can’t do in rink. Ice hockey is played in ice rink and players have skates, safety equipments and sticks witch they use to play. If you do something that is against the rules it might lead to face-off or rule breaker can get penalty witch means that team that got the penalty must play with four players for two or five minutes, depending of what rule did the player break. Ice hockey is really physical game with all the tackles and also players can start fighting, here is LINK to video. 
Ice hockey has 4 referees in one game 2 the referees and 2 linesman.