A plane is a self-contained world or universe of any size found within the multiverse. While planes can be governed by any conceivable set of rules and natural laws, or even indeed inconceivable ones, most planes visited in the storyline are comfortably similar to Earth.
There are almost infinite planes in the multiverse, separated from each other by the space known as Blind Eternities which is filled with chaotic energies, including Æther and mana. The inhabitants of most of these planes have no idea that theirs is not the only universe, or indeed the only world generally only planeswalkers know that, and are able to travel intentionally between planes.
Planes are known to "move" in relation to each other. Additionally new planes are constantly created, while others drift out of existence.
Natural planes are naturally occurring worlds that just came into existence at some point. Most known planes just have one central, populated world, and the entire plane is typically named after it. However, it is possible that in vast universes with billions galaxies and stars, other populated worlds also exist.
Notable exampls of natural planes include:
There are also artificial planes, worlds created usually by planeswalkers with sheer will. The creator of such a world define all of its rules. These planes however, are unstable and eventually collapse if there is nothing what would sustain their existence (like constant flow of mana, or technical means like flowstone).
Planechase introduced plane cards, that represent specific locations on various planes. Each plane card has a subtype corresponding to the plane the location is found on. Plane cards are the size of two regular magic cards side by side.
**309.1. Plane is a card type seen only on nontraditional Magic cards. Only the Planechase casual variant uses plane cards. See rule 901, "Planechase."
**309.2. Plane cards remain in the command zone throughout the game, both while they're part of a planar deck and while they're face up. They're not permanents. They can't be cast. If a plane card would leave the command zone, it remains in the command zone.
**309.3. Plane subtypes are listed after a long dash, and may be multiple words: "Plane — Serra's Realm." All words after the dash are, collectively, a single subtype. Planar subtypes are called planar types. A plane can have only one subtype. See rule 204.3m for the complete list of planar types.
**309.4. A plane card may have any number of static, triggered, and/or activated abilities. As long as a plane card is face up in the command zone, its static abilities affect the game, its triggered abilities may trigger, and its activated abilities may be activated.
**309.5. The controller of a face-up plane card is the player designated as the planar controller. Normally, the planar controller is whoever the active player is. However, if the current planar controller would leave the game, instead the next player in turn order that wouldn't leave the game becomes the planar controller, then the old planar controller leaves the game. The new planar controller retains that designation until he or she leaves the game or a different player becomes the active player, whichever comes first.
**309.6. A plane card is treated as if its text box included "When you roll PW, put this card on the bottom of its owner's planar deck face down, then move the top card of your planar deck face up." This is called the "planeswalking ability." A face-up plane card that's turned face down becomes a new object.
**309.7. Each plane card has a triggered ability that triggers "Whenever you roll CH." These are called "chaos abilities." Each one is indicated by a CH to its left, though the symbol itself has no special rules meaning.