The hoax has three main components -
1. The Nazis planned to exterminate the Jews.
2. The Nazis built gas chambers to exterminate the Jews and disguised them as shower rooms.
3. The Nazis killed six million Jews.

Each component of the hoax is categorically false and completely without evidence. There was no Nazi plan to exterminate the Jews or anyone else, and no evidence of one has ever been found. The gas chambers disguised as shower rooms are pure phantasmagoria, and there is not a shred of physical evidence for them. The number of Jews killed in the camps for being Jews is zero, and it is well documented that the Nazis aggressively investigated any crime in the camps.

That is the hoax, and the reality

The big lie is the photos and film footage that are shown of Jewish prisoners who had been gassed by the Nazis. The truth is that all the photos and film were taken after the war by British and US soldiers, and showed prisoners of all nationalities and religions who had died of typhus at the very last weeks of the war, primarily at Belsen where 35,000 died, 10,000 after the camp had been liberated by the British. Further, the Nazis had done everything in their power to combat the epidemic.