A cube is essentially a curated collection of MTG cards which were pre-selected by a designer to provide a balanced and diverse drafting pool.
Cube drafts typically play out like any other draft: players recieve 3 packs of 15 cards, each pack is drafted 1 card at a time, and the resulting deck is created from your draft pool and any additional basic lands you'd like to add.
However, unlike other "official" MTG formats, there are no fixed rules in cube. Cards may come from any set, have any rarity, have any power level, and have any format legality! Each designer may also choose to mix up the draft structure, or include special "house rules" which can be in effect during matches.
This format is a favorite among MTG enthusiasts for its flexibility, creativity, and the chance it gives to revisit or repurpose older cards in new ways.
Examples of Cube Types