Introduction
In the Pokemon metagame, many players rely on fast, strong and (sometimes) bulky powerhouses, Pokemons who have stats, abilities, typings and movepools that allow them to easily sweep through teams without major problems. In this categories we have Pokemons such as Gyarados, Salamence, Heatran, Lucario, Azel and Machamp. Usually, these Pokemons would be incredibly hard to deal with, specially on the hand of a skillfull player, however, there are ways to work around these huge threats, and those ways are called Status.
What is a Status?
Status are special conditions inflicted upon Pokemons when they get hit by a certian move or, in a few cases, when an ability activates that causes said Status. Some examples of moves that cause Status would be Thunderwave, Toxic, Will-O-Wisp, Hypnosis, Thunderbolt, Ice Beam or Flamethrower. Status has been, since the early days of B/R/Y a really important part of the metagame, causing many Pokemons which would usually be unstopable to become a bit easier to deal with.
Different kinds of Status
In DPP we have in total 5 "major" Status and 2 "minor" ones. The major Status, being Freeze, Burn, Paralysis, Poison and Sleep, while the minor ones are Confusion and Attract(infatuated). A Pokemon can only be affected by 1 major status at the time, and these, with really few exception (AKA, Natural Cure Pokemons) remain even after you switch. The only way to get rid of a major status is either by having the Pokemon switch (just and ONLY if its ability is Natural Cure), using the move "Aromatherapy" OR "Hell Bell", have the Pokemon hold the "Lum Berry" item, using the Hydratation ability under the Rain and some others which will be explained with more detail further ahead.
Minor Status are those 2 which can happen at the same time while a Pokemon has a major Status. Basically, this means a Pokemon can be both, Poisoned AND Confused(or any other combination or a Major Status+ 1 or both of the minor ones). These, unlike the major Status are cured upon switching, and thus are not used nearly as much as the major ones
Major Status in detail
Burn
Burn is, alphabetically speaking, the first one of the 5 major Status, and possibly one of the most useful ones for Stall teams.
Burn can be caused by a wide variety of moves, such as Heat Wave, Flamethrower, Fire Blast, Lava Plume and Will-O-Wisp among others. A Pokemon affected by the Burn condition will lose 12.5% of its health every turn AND will get its Attack Stat reduced by 50% (for example, a Pokemon with an Attack of 300 would get its Attack cut to 150 after a Burn). This makes moves such as Will-O-Wisp really common on Stall/Mixed teams, specially on Ghosts or Pokemons meant for walling physically such as Weezing, but are also often seen on Pokemons of a more offensive nature such as Heatran
The only Pokemons inmune to Burns are Fire Type Pokemons, Pokemons with the Flash Fire ability, Pokemons with the Water Veil ability and Pokemon with the Leaf Guard ability under the sun. To cure a Burn Status you can either use any of the options on the "Different Kind of Status" on this guide or have the Pokemon hold the item Rawst Berry. Pokemon with Magic Guard will have their attack cut by half, but wont get hurt by Burn
Freeze
Freeze is, by far, the rarest of all Status. The reason for this is that there is not a single move that has a 100% Freeze chance (unlike Burn, Sleep, Paralysis and Poison). A Pokemon frozen is unable to do anything but to switch in a period which varies, but usually doesnt go by more than 7 turns . There are really few moves that can cause the Freeze Status, with Ice Beam, Blizzard, Ice Punch, Tri-Attack and Ice Fang being the most common.
The only Pokemons inmune to Freeze are those of the type "Ice" and Pokemons with the Magma Armor ability. To cure a Freeze you can wait for the Pokemon to thaw by itself, waiting to get hit by a Fire move or, if the Pokemon has access to it, to use Flame Wheel or Sacred Fire
Paralisys
Paralysis is probably the most common status move for offensive teams. A paralysed Pokemon has its speed cut to a 25% of its original, and also has a 25% chance of getting "Fully Paralyzed", which means the Pokemon wont be able to do anything that turn. The most common way to inflcit a Paralysis Status is by using Thunderwave or moves which secondary effect cause Paralysis, such as Thunderbolt, Thunder, Thunderpunch, Bounce or Body Slam.
The only Pokemons unaffected by Paralysis are Pokemons with the Limber ability. Pokemons with the Quick Feet ability are not slow down by Paralysis status, but still have a 25% chance of getting fully Paraliyzed. Pokemon with Magic Guard will get slow down, but never fully paralyzed.
Poison
Poison is a status cause mainly by Poison moves (duh). Poison can be divided in 2 types: Normal Poison and Badly Poison. Normal Poison causes a damage of 12.5% per turn, and is caused only by a handful of moves, with the most common being Sludge Bomb. However, considering the awful coverage and that Burn causes the same damage while reducing an opponent attacking stat, normal Poison is rarely used. Badly poison, on the other hand, causes a damage of 1/16, which increased every turn. This means that the first turn it will 1/16 of damage, the secon 2/16, the third 3/16 and so on until it reaches a damage of 15/16. This makes Toxic and Toxic Spikes really common moves on Stall Teams.
The only Pokemons inmune to Poison and Steel and Poison types, although Levitators and Flying type Pokemons are unaffected by Toxic Spikes. To cure a Poison you can use a Pecha Berry or any of the Status cure moves. To get rid of Toxic Spikes you need to switch in a non-flying, non-levitaror Poison type, who will absorb them, Rapid Spin also works
Sleep
Sleep is a Status condition that can be caused by moves such as Hypnosis, Spore, Sleep Powder and Rest. Sleeping Pokemons wont do anything in a period no longer than 7 turns. This number can be cut by half by Pokemons with the Early Bird ability.
To cure a Sleep, you can use a Chesto Berry, wait for the Pokemon to wake up by itself or use the Status curing moves. Pokemons with the Ability Insomnia and Vital Spirit cant be put to sleep
Minor Status
Confusion
Confusion is a Minor status caused by moves such as Confusion on Confuse Ray. A Pokemon affected by Confusion has a chance of 50% of hitting itself during its confusion. Pokemons with the Own Tempo ability cant be confused. To cure a Confusion you can either wait for it to vanish or switch
Infatuation
Infatuation is the other minor Status, caused exclusively by the move Attract or the ablity Cute Charm. The Pokemon who induces it must be from the opposite sex to the one going to get Infatuated. A pokemon affected by this has a 50% chance of doing nothing, kind of like confusion, but without the damaging part. To cure a Infatuation you can either switch or wait for it to vanish.
It worthy to note that every Status move can be blocked by the use of Substitute. Any question or doubts, post here and I´ll do my best to answer your questions
