In order for a creature to gain the Pinned condition, it must first have the Restrained or Prone condition active as a pre-requisite.
A creature that has gained the Pinned is unable to move or make physical attacks, but can still speak and cast spells. The difference between Pinned and Paralyzed is the method of remedying these conditions is different. The Pinned creature may attempt a Break Free action to release themselves. A Pinned creature automatically fails Dexterity challenges.