306.1 A player who has priority may cast a planeswalker card from their hand during a main phase of their turn when the stack is empty. Casting a planeswalker as a spell uses the stack. (See rule 601, “Casting Spells.”)
306.3 Planeswalker subtypes are always a single word and are listed after a long dash: “Planeswalker — Jace.” Each word after the dash is a separate subtype. Planeswalker subtypes are also called planeswalker types. Planeswalkers may have multiple subtypes. See rule 205.3j for the complete list of planeswalker types.
306.4 Previously, planeswalkers were subject to a “planeswalker uniqueness rule” that stopped a player from controlling two planeswalkers of the same planeswalker type. This rule has been removed and planeswalker cards printed before this change have received errata in the Oracle card reference to have the legendary supertype. Like other legendary permanents, they are subject to the “legend rule” (see rule 704.5j).
306.5b A planeswalker has the intrinsic ability “This permanent enters with a number of loyalty counters on it equal to its printed loyalty number.” This ability creates a replacement effect (see rule 614.1c).
306.5d Each planeswalker has a number of loyalty abilities, which are activated abilities with loyalty symbols in their costs. Loyalty abilities follow special rules: A player may activate a loyalty ability of a permanent they control any time they have priority and the stack is empty during a main phase of their turn, but only if none of that permanent’s loyalty abilities have been activated that turn. See rule 606, “Loyalty Abilities.”
306.7 Previously, planeswalkers were subject to a redirection effect that allowed a player to have noncombat damage that would be dealt to an opponent be dealt to a planeswalker under that opponent’s control instead. This rule has been removed and certain cards have received errata in the Oracle card reference to deal damage directly to planeswalkers.