Wolfenstein 3D is a 1992 first-person shoter that was developed by ID Software and published by Apogee Software for the DOS system. It was inspired by the games Castle Woflenstein and Beyond Castle Wolfenstein (both developed by Muse Software) and was originally released as Shareware making it available to freely copy (but it only had the episode Esacpe from Castle Wolfenstein) before it became commercially available.
The Retail version of the game came with three episodes called Escape from Castle Woflenstein, Operation Einfaust and Die Fuhrer, Die. These episodes followed a storylineset in the heart of Nazi Germany. You are an American spy named B.J. Blazcowitz who is tasked with finding information about the secret Operation Einfaust
The game was a critical and commercial success and it is considered as the game that launched FPS games