Short answer: Jews, 'gypsies' (Romanies and Sinti), Soviet prisoners of war, Communists, liberals, other political dissidents, incurables, Jehovah's Witnesses and homosexuals.
When used by professional historians the term the Holocaust generally refers specifically to the genocide of the Jews.
Although the Jews were targeted by Nazis, there were many others who are often overlooked. The Nazis wanted 'Lebensraum' (meaning 'living space') to the east, so each of the eastern countries bordering Germany was targeted (at least for enslavement). The Polish people were among the victims of the Nazi extermination, referred to in this 22 August 1939 speech excerpt from Adolf Hitler to Reichmarshal Hermann Goering and the commanding generals at Obersalzberg:
"Our strength consists in our speed and in our brutality. Genghis Khan led millions of women and children to slaughter - with premeditation and a happy heart. History sees in him solely the founder of a state. It's a matter of indifference to me what a weak western European civilization will say about me.
I have issued the command - and I'll have anybody who utters but one word of criticism executed by a firing squad - that our war aim does not consist in reaching certain lines, but in the physical destruction of the enemy. Accordingly, I have placed my death-head formations in readiness - for the present only in the East - with orders to them to send to death mercilessly and without compassion, men, women, and children of Polish derivation and language. Only thus shall we gain the living space (Lebensraum) which we need. Who, after all, speaks today of the annihilation of the Armenians?"
Please see the related question below.
All the Jews of Europe were systematically targeted for murder by the Nazi regime. The Nazis considered Jews a “mortal threat” to the German “race.”
The main victims were Jews from all the nations invaded by the Nazis.
Please see the related questions.
the victims were the armenians and the perpetrators are the nazis
people who didnt believe in his rule and Jewish People
each group had its reasons for being targeted, you need to specify which you want to know about.
The Nazis did not target Muslims. That is one of those myths.
Nazis deliberately killed about 12 millions people, half of them Jews, other large groups of their victims include Roma (Gypsies) and Soviet POWs Millions more died as a result of war they started.
The Nazis found that it was the easiest way of disposing of the corpses of their victims.
The Nazis had bottomless contempt for the Russians.
Yes they were one of the groups targeted and abused by Hitler and the Nazis and suffered in the concentration camps.
That is a matter of semantics, historians say no one, that the gypsies suffered their own genocide. But for us who know less, we like to call all of the victims of the Nazis as victims of the Holocaust._____The trouble is that there are at least two competing definitions of the Holocaust. Practically all professional historians use the term specifically for the Nazi genocide of the Jews in World War 2. However, there is also a popular definition, especially in the US, which includes all victims of mass murder by the Nazis and even groups that the Nazis persecuted. As far as I'm aware, (partial) public funding for the United States Holocaust Memorial Museum (USHMM) led other groups that had suffered - often grievously - under the Nazis to claim that they should be included. Soon it became a bit of a bandwagon. Please see the related question.