901.11 After the game has started, if a player moves the top card of their planar deck off that planar deck and turns it face up, that player has “planeswalked.” Continuous effects with durations that last until a player planeswalks end. Abilities that trigger when a player planeswalks trigger. See rule 701.31.
901.11a
A player may planeswalk as the result of the “planeswalking ability” (see rule 901.8), because the owner of a face-up plane card or phenomenon card leaves the game (see rule 901.10), or because a phenomenon’s triggered ability leaves the stack (see rule 704.6f). Abilities may also instruct a player to planeswalk.
(refs: 901.8, 901.10, 704.6f)
901.11b
The plane card that’s turned face up is the plane the player planeswalks to. The plane card or phenomenon card that’s turned face down, or that leaves the game, is the plane or phenomenon the player planeswalks away from.
901.11c
If a player planeswalks when there is more than one face-up plane card, that player planeswalks away from all such planes.