Hidden history has some documentation to back it up. Or contains information that can be attributed to being authentic to the person who recorded it.

Conspiracy theories are ideas which have no historical or social effects long term.

There needs to be evidence for it to be considered hidden history

No. I mean the kind of history that governments and other organisations don't want most people to know.

I gave more than a couple of examples as to what classifies as hidden history. Just anything that you've come across in mainstream history that made you go "that doesn't add up"

Like for me, gassing jews, cremating them, etc. just didn't add up for me during ww2. Why would a nation at war waste valuable resources to kill some civilian prisoners? Why waste the chemicals to kill them and the fuel to burn them when you could easily shoot them, starve them or let them freeze out in the open?

It's a waste of resources. I then found reports that the soviets built the chimneys at the camps and knocked down walls to make them look like chambers. But the doors were made of wood. Who makes a gas chamber with wooden doors?
Plus Hitler was a soldier in WW1 and we all know that anyone who has witnessed war would never want to repeat it unless they had a very good reason. This led to me wondering what the original purpose of the war was. Which led me to the Treaty which stated that 1) Germany and all it's media outlets could not publish any official documents until 2099 unless the allies allowed it (Control of media). 2) Each German chancellor must pledge allegiance to the USA before entering office. Sounds dodgy right?

So whatever history you think most people don't know about. The really high quality stuff that governments hate people knowing.

Holocaust denial is the act of denying the genocide of Jews in the Holocaust during World War II. Holocaust denial often includes the following claims: that Nazi Germany's Final Solution was aimed only at deporting Jews from the Reich, but that it did not include the extermination of Jews; that Nazi authorities did not use extermination camps and gas chambers to mass murder Jews; or that the actual number of Jews killed was significantly lower than the historically accepted figure of 5 to 6 million, typically around a tenth of that figure
. [en.wikipedia.org]

As I said. The holicaust happened. I just have trouble believing that Germans, who had and still have some of the best engineers in the world. Would waste time, resources, energy and money to kill people in a gas chamber. There are falsified testimonies from Russian soldiers, undeniable structural evidence, lack of logical reasoning. All I'm saying is why would the Germans waste more than they had to to kill some Jews.

I have nothing against the Jews. I believe they're just as bad as the Christians and Muslims.