The trading card game Magic: The Gathering has released a large number of sets since it was first published by Wizards of the Coast. After the 1993 release of Limited Edition, also known as Alpha and Beta, roughly 3-4 major sets have been released per year, in addition to various spin-off products.
Magic has made three types of sets since Alpha and Beta: base/core sets, expansion sets, and compilation sets. Expansion sets are the most numerous and prevalent type of expansion; they primarily consist of new cards, with few or no reprints, and either explore a new setting, or advance the plot in an existing setting. Base sets, later renamed core sets, are the successors to the original Limited Edition and are meant to provide a baseline Magic experience; they tended to consist either largely or entirely of reprints. Compilation sets also exist entirely of reprints, and tend to be made as either a special themed product, or as a way to increase supply of cards with small printings. Examples of compilation sets with randomized boosters include Chronicles and Modern Masters. There also exist compilation products with a pre-selected and fixed card pool, such as the Duel Decks and From The Vault series. Theme decks serve a similar function; however, they are always attached to a specific set or block, while compilations are free to pick and choose cards from any set.
All expansion sets, and all editions of the base set from Sixth Edition onward, are identified by an expansion symbol printed on the right side of cards, below the art and above the text box. From Exodus onward, the expansion symbols are also color-coded to denote rarity: black for common and basic land cards, silver for uncommon, and gold for rare. Beginning with the Shards of Alara set, a red-orange expansion symbol denotes a new rarity: "Mythic Rare" (the Time Spiral set featured an additional purple coloration for "timeshifted" cards). For the early expansion sets (from Arabian Nights to Alliances), the rarities of cards were often much more complicated than the breakdown into common, uncommon, and rare suggests. Cards in compilations are assigned partially arbitrary rarity by Wizards, with some cards assigned rare status and some assigned mythic rare in a given set.
Base/core set editions
After the second version (Beta) of the first set, which contained two cards mistakenly excluded from the first version (Alpha), all subsequent base sets through 10th Edition consisted of cards that had been printed before in either the original base set or an expansion set. Alpha through Fifth Edition did not have set symbols printed on the actual cards, though those sets were retroactively given set symbols in Wizards of the Coast's official Gatherer database of Magic cards.
Expansion sets
Expansion sets from Ice Age to Rivals of Ixalan (with the exception of Homelands) came in groups called "blocks". Blocks were cohesive products: they usually centered around one plane, followed a particular storyline, and contained cards and mechanics that supported both. Blocks generally consisted of one large "stand-alone" expansion set of 250-380 cards, followed by one or two small expansion sets of 141-200 cards which continue the themes introduced in the large set. Like the base set, stand-alone expansion sets contain basic land cards; other expansion sets do not. Beginning with Alliances, expansion sets were given codenames while in development; the code names of the expansions of a block usually fit together to form a phrase or common theme. Ice Age, Homelands, and Alliances were retroactively declared a block at some point, despite Homelands not being connected to the other two in any way. In 2006, WotC retroactively dropped Homelands from the Ice Age cycle and added Coldsnap to it. With the Zendikar cycle in 2009, the traditional large-small-small block structure began to be varied, with some blocks including a second large set later in the cycle. Starting with the Battle for Zendikar block in 2015, the default structure of a block was changed to large-small, with two blocks released per year and each block consisting of only two sets.