Status Ailment
Status ailments affect a Pokémon's ability to battle. There are two kinds of status. The first are non-volatile and the second are volatile.
Non-volatile status
Non-volatile status ailments are status ailments that will remain until a Pokémon is healed at a Pokémon Center, a specific curative item is used, or, in case of freeze and sleep, after a certain number of turns during the battle. A Pokémon inflicted with a non-volatile status will still be affected after being pulled out of battle (unless they have the Natural Cure Ability), and after a battle is over. It is only possible for a Pokémon to be afflicted by one of these at a time.
Burn
The burn condition (BRN) halves damage dealt by a Pokémon's physical moves. Additionally, at the end of a turn, the Pokémon loses 1/8 its maximum hit points.
Freeze
The freeze condition (FRZ) causes a Pokémon to be unable to make a move. Damaging Fire-type moves used on a frozen Pokémon will remove the freeze status. Freeze has a random, 20% chance to be cured on its own on the frozen Pokémon's turn.
Paralysis
The paralysis condition (PAR) causes a Pokémon to be unable to attack a quarter of the time. Additionally, its Speed is reduced by 25%.
Poison
The poison condition (PSN) causes a Pokémon to lose 1/8 of its maximum hit points every turn. Steel- and Poison-type Pokémon and Pokémon with the Immunity Ability cannot be poisoned.
Bad Poison
The badly poisoned condition is caused by Toxic and Poison Fang, as well as by Toxic Spikes after it is used twice. It is the same as Poison except its damage begins at 1/16 and grows an additional 1/16 every turn.
Sleep
A Pokémon that is asleep (SLP) is immobilized and can only use the moves Snore and Sleep Talk. Sleep lasts for a randomly chosen duration of 1 to 3 turns. A Pokémon can inflict self-induced sleep using the move Rest.
Volatile status
A volatile status will wear off when a Pokémon is taken out of battle or a battle is over. Many of these will also wear off after a number of turns pass. Since they aren't shown in battle as a status ailment (having an icon) a Pokémon can be affected with multiple volatile ailments and a non-volatile aliment at the same time.
Confusion
The confused condition causes a Pokémon to hurt itself in its confusion 50% of the time. The damage is done as if the Pokémon attacked itself with a 40-power typeless physical attack.
Confusion wears off after 1-4 attacking turns.
Flinch
The flinch status is a one-turn status that prevents a Pokémon from attacking. A Pokémon can only flinch if the opponent attacks first.
Infatuation
A Pokémon that is infatuated cannot attack 50% of the time, even against Pokémon other than the one it is infatuated with.
Infatuation will end as soon as either the affected Pokémon or the Pokémon it is attracted to is removed from the battle.