Type II Magic: The Gathering tournaments, often called "standard" tournaments, are constructed-deck: that is, the deck a competitor plays with is assembled by that competitor out of his own card collection according to certain rules of card eligibility. The specifics of these rules change over time, but their general outlines are not complicated.
General Tournament Rules
All "constructed-deck" Magic tournaments require a player to provide his own deck of at least 60 cards. There is no maximum deck size. A player may also construct a "sideboard" of exactly 15 cards, which he can exchange on a one-for-one basis for cards in his deck between tournament matches. Unless the card specifies otherwise, an eligible deck/sideboard set may contain no more than four copies of a specific card.
Card Use Guidelines
While Type I ("vintage") tournaments allow every official Magic card ever printed, Type II tournaments allow a much smaller set of cards to be used in deck creation. Allowable cards include those in the current basic edition and those in the two most recent blocks of expansion sets. So for instance, Type II Tournaments in May 2010 allow cards from Magic 2010 (the basic set) and the Zendikar and Alara expansion blocks: the expansions Shards of Alara, Conflux, Alara Reborn, Zendikar, Worldwake, and Rise of the Eldrazi.
Restricted and Banned Cards
Certain cards in Magic tournaments may be restricted (only one appearance per deck is allowable) or outright banned. As of May 2010, Type II tournament rules neither restrict nor ban any cards. For the most up-to-date information possible, check the Wizards of the Coast website (link in "Resources".)
Tags: Magic tournaments, tournaments allow