Plane Shift
Plane Shift refers to one of two things in relation to Dungeons & Dragons: a spell that has been around since at least the creation of Advanced Dungeons & Dragons, or a series of articles released by Wizards of the Coast in support of Dungeons & Dragons 5th Edition.
The Spell
The Plane Shift spell is a magic spell available to both clerics and wizards in Dungeons & Dragons. A high level spell - 5th level Cleric/7th level Wizard in 3e, a 7th level spell available to Clerics, Druids, Sorcerers, Warlocks and Wizards in 5e - it allows the caster to transfer themselves and/or other beings from one plane to another. It is technically more difficult to access than portals, and not always perfect, but in a pinch, it can be a life-saver.
The Articles
The Plane Shift article series examines the various planes of Magic: The Gathering and provides advice to DMs on how to use Magic content, especially material from that particular plane, in their games of D&D. These articles usually include new playable races and new monsters, and may on occasion include new subclasses, magic items or other mechanics.
Currently, there have been five releases in the series, covering the planes of Zendikar, Kaladesh, Innistrad, Amonkhet and Ixalan.