A Parry, when executed at the proper time, will deflect an enemy's attack and put it in a staggered state, and as such, subject to a critical attack or Riposte.
Some enemies in the game cannot be parried, although they can be staggered once their poise is broken, also rendering them open to be riposted.
A Parry is executed by pressing the Left Strong Attack button ( / ) with a shield or weapon that has the "Parry" skill. Shields that can parry will have a small circular icon depicting a shield in the lower corner. Specific shields have a longer "parry window", such as the Buckler or the Target Shield.
A Riposte can be executed after a parry, or in some cases after the enemy's poise is broken, to deal critical damage. This is done by approaching them in their staggered animation and pressing the Right Weak Attack button ( / ), either one- or two-handed.
Certain enemies can be staggered instantly and become open to be riposted by successfully landing on their heads. Examples include dropping from an elevated platform on top of an Elder Ghru in the Farron Keep or dropping on top of a Sulyvahn's Beast from the ladder in the Water Reserve.