>>45823537>>45823624Terrains effects only apply to grounded Pokemon. Pokemon with the ability levitate Pokemon that are flying type, etc. won't be effected by terrains. This doesn't apply if gravity is in effect or if a Pokemon is hit by smack down since that gives the "grounded" status.
Psychic terrain blocks priority moves from hitting Pokemon who are effected by the terrain. It also boosts the power of psychic type moves.
Electric terrain blocks the sleep status effect from Pokemon that are effected by the terrain. It also boosts the power of electric type moves.
Grassy terrain restores HP of Pokemon who are effected by the terrain. It also boosts the power of grass type moves.
Misty terrain prevents all status effects from Pokemon who are effected by the terrain. It also halves the power of dragon type moves.
Some items (e.g. terrain extender, grassy seed, misty seed, etc.) have special effects when used with terrain setting moves or abilities, and some moves (expanding force, grassy glide, etc.) have special effects when a terrain is in effect.
>>45823625Zygarde 100% was never in Gen 6. You're probably thinking of Thousand Waves and Thousand Arrows.