Despite being part of legal sets, the following cards are explicitly not allowed in decks for this format.
Standard is a tournament format containing several recent Magic: The Gathering sets. Most sets enter the format when they're released and drop out about twenty-one months later.
The rotating group's size generally grows to eight, then—with the next joining release—drops its oldest four sets. The joining set is added as a fifth, and the pool's size slowly grows to eight again, repeating the cycle. There are exceptions to this. It's confusing.
A Standard deck contains 60+ Standard cards and can optionally have a sideboard of up to 15 additional such cards. Apart from basic lands, the combined main deck and sideboard cannot have more than four copies of any card.
Brawl is a format based on Standard—all rotations listed here apply to Brawl as well—but Brawl has its own banlist.
Not all sets enter Standard upon release. For example, Masters sets and Commander sets never enter the format.