Generation VI, what changed

Generation VI added the Fairy type and Mega Evolution

In review Under fact check; out of search until accepted.

Generation VI added Fairy, the first new type since Dark and Steel in 1999, which brought the chart to 18 types. X and Y went on sale worldwide on 12 October 2013 for the Nintendo 3DS, the first main-series games released on the same day in every region, and added 72 species for a total of 721 in 3D models. Omega Ruby and Alpha Sapphire remade the Hoenn games in 2014.

Generation VI: X, Y, Omega Ruby and Alpha Sapphire. Main-series games only.

Types18

Stat formulaIVs, EVs (252 per stat), nature

Physical and specialBy move

BreedingDay Care, Destiny Knot passes five IVs

Battle mechanicMega Evolution, terrain

GamesX, Y, Omega Ruby, Alpha Sapphire

The defining change

Fairy brought the chart to 18 types

Fairy beat Fighting, Dragon and Dark, was resisted by Fire, Poison and Steel, and was immune to Dragon.
Older species were retyped: Clefairy and Togepi became pure Fairy, Jigglypuff became Normal and Fairy, and Marill became Water and Fairy.

Steel lost two resistances and new immunities appeared

Steel lost its resistance to Ghost and to Dark.
Dragon-type moves had no effect on Fairy types, the first immunity against Dragon.
Grass types became immune to powder moves, and Electric types to paralysis.

Critical hits fell to 1.5 times damage

Critical hits dropped from 2 times to 1.5 times damage.
Gems were cut to 1.3 times, and only the Normal Gem stayed obtainable.
Weather from abilities lasted five turns, or eight with the matching rock.
Several older species received higher base stats, such as Pikachu's Defense from 30 to 40.

The Destiny Knot passed five IVs and shiny odds doubled

A Destiny Knot passed five IVs from the parents instead of three.
The mother passed her Poké Ball, and either parent passed egg moves.
Shiny odds improved to 1 in 4,096.
Super Training let players set EVs directly, with a per-stat cap of 252.

Mega Evolution and terrain arrived

Mega Evolution arrived, once per battle, raising base stats by 100.
Electric, Grassy and Misty Terrain arrived.
Pokémon-Amie added an affection value with battle effects.
Horde encounters, Sky battles and Inverse battles arrived.

The Exp. Share began covering the whole party

The Exp. Share became a switch that shared experience with the whole party.
Ghost types became able to switch out of any trapping move or ability.
Most legendary encounters came with at least three maximum IVs.

Omega Ruby and Alpha Sapphire added Primal Reversion

X featured Xerneas and Y featured Yveltal.
X and Y had paired exclusive Mega Stones for Charizard and Mewtwo.
Omega Ruby and Alpha Sapphire added Primal Reversion for Groudon and Kyogre and the Delta Episode.
Omega Ruby and Alpha Sapphire raised the Mega Evolution count to 48 forms across 46 species.

2 releases, 2013 to 2014

2013X and YNintendo 3DS
2014Omega Ruby and Alpha SapphireNintendo 3DS

Type chart era

18 types in the Generations VI to IX chart

Battles in these games follow that chart, shared with the rest of Generations VI to IX. Open the type chart by era

Generation VI starts the 18-type matchup column

The Gen VI and later matchup column uses the 18-type chart with Fairy and without Steel's Ghost and Dark resistances.
The type history block shows Fairy retypes with a Gen VI boundary, such as Clefairy from Normal to Fairy.
The forms block lists Mega forms with their own stats and abilities.
Learnset tabs X-Y and Omega Ruby-Alpha Sapphire show egg moves that either parent can pass.