The terrain moves (Grassy Terrain, Electric Terrain and Misty Terrain) are... "unique" moves. Taking a leaf out of Safeguard's book, these all have effects which benefit pokemon on the field, except with two key differences: they a: affect all grounded (non Flying-type/levitating/Air Balloon/under the effects of Magnet Rise/under the effects of Telekinisis) Pokémon on the field rather than just your side, and b: they have hidden effects. Here are "complete" the descriptions of the moves:
Grassy Terrain: Grassy Terrain creates terrain that restores the HP of grounded Pokémon by 1/16 of their max HP at the end of each turn and increases the power of Grass-type moves used by grounded Pokémon by 50%. If Grassy Terrain is in effect, Nature Power becomes Energy Ball, Secret Power uses the animation of Vine Whip and may cause sleep, and Camouflage causes the user to become Grass-type. In addition, the power of Earthquake, Bulldoze, and Magnitude is halved, even in a single battle. When Grassy Terrain is active, Pokémon with the ability Grass Pelt have their Defense stat boosted to 1.5x its usual value. It's effects fade after five turns, including the turn in which the move is used.
Electric Terrain: Electric Terrain creates terrain that prevents any Pokémon on the ground from falling asleep and increases the power of Electric-type moves used by grounded Pokémon by 50%. It causes Yawn to fail if used on a grounded Pokémon, and prevents grounded Pokémon already drowsy due to Yawn from falling asleep. Rest will also fail when used by a grounded Pokémon. If Electric Terrain is in effect, Nature Power becomes Thunderbolt, Secret Power uses the animation of Thunder Shock and may cause paralysis, and Camouflage causes the user to become Electric-type. It's effects fade after five turns, including the turn in which the move is used.
Misty Terrain: Misty Terrain creates terrain that prevents non-volatile status conditions (status conditions which don't disappear upon switch-out, i.e. Poison, Bad Poison, Burn, Paralysis, Sleep and Freeze) and halves the damage taken from Dragon-type moves by Pokémon on the ground. It causes Yawn to fail if used on a grounded Pokémon, and prevents grounded Pokémon already drowsy due to Yawn from falling asleep. If Misty Terrain is in effect, Nature Power becomes Moonblast, Secret Power uses the animation of Fairy Wind and may lower its target's Special Attack, and Camouflage causes the user to become Fairy-type. It's effects fade after five turns, including the turn in which the move is used.
I believe that, while their use is limited, they only have use in the doubles format due to the short-term nature of the moves.
And... discuss!
Grassy Terrain: Grassy Terrain creates terrain that restores the HP of grounded Pokémon by 1/16 of their max HP at the end of each turn and increases the power of Grass-type moves used by grounded Pokémon by 50%. If Grassy Terrain is in effect, Nature Power becomes Energy Ball, Secret Power uses the animation of Vine Whip and may cause sleep, and Camouflage causes the user to become Grass-type. In addition, the power of Earthquake, Bulldoze, and Magnitude is halved, even in a single battle. When Grassy Terrain is active, Pokémon with the ability Grass Pelt have their Defense stat boosted to 1.5x its usual value. It's effects fade after five turns, including the turn in which the move is used.
Electric Terrain: Electric Terrain creates terrain that prevents any Pokémon on the ground from falling asleep and increases the power of Electric-type moves used by grounded Pokémon by 50%. It causes Yawn to fail if used on a grounded Pokémon, and prevents grounded Pokémon already drowsy due to Yawn from falling asleep. Rest will also fail when used by a grounded Pokémon. If Electric Terrain is in effect, Nature Power becomes Thunderbolt, Secret Power uses the animation of Thunder Shock and may cause paralysis, and Camouflage causes the user to become Electric-type. It's effects fade after five turns, including the turn in which the move is used.
Misty Terrain: Misty Terrain creates terrain that prevents non-volatile status conditions (status conditions which don't disappear upon switch-out, i.e. Poison, Bad Poison, Burn, Paralysis, Sleep and Freeze) and halves the damage taken from Dragon-type moves by Pokémon on the ground. It causes Yawn to fail if used on a grounded Pokémon, and prevents grounded Pokémon already drowsy due to Yawn from falling asleep. If Misty Terrain is in effect, Nature Power becomes Moonblast, Secret Power uses the animation of Fairy Wind and may lower its target's Special Attack, and Camouflage causes the user to become Fairy-type. It's effects fade after five turns, including the turn in which the move is used.
I believe that, while their use is limited, they only have use in the doubles format due to the short-term nature of the moves.
And... discuss!