The Witcher is a highly popular game developed by CD Projekt Red and published by Atari. In the game, story takes place in a medieval fantasy world follows Geralt of Rivia one of Witchers (monster hunters with have super powers). There are 3 sequels to The Witcher franchise titled The Witcher 2: Assassins of Kings and The Witcher 3: Wild Hunt.
Netflix has acquired the rights to produce a tv show based on the game. It is set to release between October and November of this. Not much is know about the plot yet. The trailer has not been released yet. The show is currently being filmed in Hungary.