What is a sideboard?

    A sideboard is a group of 15 cards that add in after a game of a match.  If you play casual, sideboards are not necessary.   In most tournaments, it is smart to have a sideboard.  It must be 15 cards, no more or no less.  Usually the cards are for against certain color or strategy decks. 

    Sometimes you can just put in a card to substitute for a card that doesn't do well against the opposing deck.  For example: You may put in a card that does well against any deck for a card that has little or no effect on the opposing deck, like a Necropotence against a burn deck.  Some of the best sideboard cards are ones that deal mass damage to creatures of the certain color or toughness like Earthquake for weenies.  Some cards like Hydroblast, Pyroblast and the Red and Blue elemental blasts are good too.

    You sideboard after a game has finished.  After the second game is over, you may choose to sideboard again.  Basically, for each game you play, after the game, you may choose to change the sideboarded cards.  Cards in the sideboard count just like part of the deck.  You may not have 4 of the same card in the sideboard and 4 again in the main deck.  You may though, have 2 in sideboard and 2 in the deck.  In conclusion, you may not have more than 4 of a card in the deck and sideboard combined.