1) It is not possible to explain it in a simple way, because it is a little complicated. 2) Here a basic definition: "In ice hockey, play is said to be offside if a player on the attacking team enters the attacking zone before the puck itself enters the zone, whether it is being carried by a teammate or otherwise sent in across the blue line. When an offside violation occurs, the linesman blows the play dead, and a faceoff is conducted in the neutral zone closest to where the offside was." Notice that you will not understand what happens if you don't know what are: - the attacking zone - the blue line - a linesman - a faceoff - the neutral zone 3) Who talked here about the skates? Nobody. However, you will not understand offside without the skate position. What does it mean that the player or the puck is inside the attacking zone? It must be better defined: "There are two determining factors in an offside violation: Attacking players' skate position: One of a player's skates is not in contact with or behind the blue line of the attacking zone before the puck enters that zone. Puck position: The puck must completely cross the outer edge of the blue line to be considered inside the attacking zone for the purposes of offsides." 3) At this point, a player could also put themselves offside. However, this will not be considered as offside: "Note that the puck must enter the attacking zone for an offside call to be made; a player being over the line does not result in an offside call until the puck crosses the line, and that a player cannot put himself offside, such as by carrying the puck in while skating backwards." 4) You thought that was it? Not at all! Now we deal with the really interesting things. Interesting also, because the rules could here differ from one league to the other: "Though the basic offside rule is always the same, there are different rules for the situation when the puck is shot in while a player is offside, but the defending team gains control of the puck. With immediate offside, play is dead the instant an offside violation occurs. (Used in USA Hockey youth leagues) Delayed offside allows the defending team a chance to move the puck out of the zone. The play remains offside until the puck enters the neutral zone. Play is blown dead if the defending team does not attempt to move the puck forward. (Used in the major North American leagues from until 2004 (AHL, except 1986-96) and 2005 (ECHL, from 1996-2005), and NHL before 2005 rule changes.) Tag-up offside is a variation of delayed offside. In a delayed offside situation, if each attacking player who is offside "tags up" by making skate contact on or behind the neutral zone, the delayed offside becomes negated. (Used in NCAA, Hockey Canada, the IIHF, USA Hockey junior leagues, some North American professional leagues, adult leagues, and the NHL from 1986-1996, and once again after the 2005 Collective Bargaining Agreement.)" 5) Now you think you know everything about offside? I am rolling on the floor laughing! You must also consider this: "Play is stopped immediately if a player from the attacking team touches the puck in the attacking zone while he or any of his teammates is offside." Moreover, all the above was only referring to a particular kind of offside (the main kind, I admit). There is also another one: "Offside is also used to refer to a player lining up on his opponent's side during a faceoff. There is no penalty for this, though the faceoff may not be conducted while a player is offside." Quite interesting. We are now talking about a totally new concept, the *penalty*. It looks like the definition of the "normal" offside forgot to mention the fact that if there was an offside, there was also a penalty. 6) Of course, we were just talking about offside. What you just learned here will not help you much to understand what is an "offside pass". And maybe there are some people who will explain this to you very differently, because they did not notice that there are actually two offside rules, the tag-up offside vs. the old offside rule. And I suppose this only applies to men's ice hockey, anyway. Forget the whole stuff if you are talking about - Offside (association football/soccer) - Offside (American and Canadian football) - Offside (rugby) - Offside (field hockey) Source and further information: http://en.wikipedia.org/wiki/Offside_%28ice_hockey%29

To be brief, the rinks are the same size in both leagues and to simplify the offside rule, just know that an attacking player can not cross the opponent's blue line before the puck