There a number of special Status Ailments which affect Pokémon in various ways. These can be caused by a number of ways, most notably moves, such as Sing.
Just like they can be caused, they can also be cured. Some moves can cure them; but items and healing your Pokémon at a Pokémon Center are the primary ways to cure status ailments.
The primary ailments are as follows:
|Burn||The Pokémon takes some damage at the end of every turn and their Attack stat falls drastically.||Burn Heal|
|Freeze||The Pokémon cannot perform any action. Cures naturally after a number of turns in battle. Upon thawing; the Pokémon will immediately perform its selected move.||Ice Heal|
|Paralysis||The Pokémon sometimes cannot move, therefore losing their turn, and their Speed stat falls drastically.||Parylz Heal|
|Poison||The Pokémon takes some damage at the end of every turn.||Antidote|
|Sleep||The Pokémon cannot perform any action. Cures naturally after a number of turns in battle. Upon waking; the Pokémon will immediately perform its selected move.||Awakening|
Note: These ailments transfer between battles and can be quite irritating unless dealt with as soon as possible. Of course, your Pokémon aren't the only ones that can inflict status ailments so make sure you're using them against your opponents too!