The Holocaust was so significant in WW2 because 15 million people died in the concentration camps and half of them were Jews alone.
To be clear, the broader definition of the Holocaust - which includes not just Jews, but other racial groups, such as the Roma and Poles, and also the extermination of gays and mentally ill - does NOT include those merely "mistreated" to death (e.g. Russian POWs and those sent to the camps for political reasons). The Holocaust is concerned with the intentional systematic attempt to exterminate all segments of a specific group, identifiable by certain "racial" or "inherent" traits. Merely being killed as an "enemy of the state" does not qualify one as being a victim of the Holocaust. As such, the broad definition of the Holocaust encompasses a total death toll around 9 million. Additional deaths of Soviet POWs and civilians, Jehovah's Witnesses, Catholics, anti-Nazi politicians and activists, and communists are certainly victims of Nazi persecution (and number between 5-10 million), but aren't really part of the systematic, intentional policy of racial "cleansing" which is the root of the Holocaust.
Besides the sheer numbers of deaths involved, the other historically significant marker of the Holocaust is that it was the first time (and, so far, the last time) that an industrialized nation attempted a genocide using the full organization and industry of the state itself. Both before and after, genocides have been committed by mostly unorganized forces, generally at the encouragement of the government. In the cases where the genocidal forces were actually well-organized, they were nonetheless never officially recognized or supported by the government. That is, the unique characteristic of the Nazi-run Holocaust was that the genocide was not only incredibly well organized and committed by official government forces, but that it was both official government policy AND a part of the actual government bureaucracy. The terror here is that this level of official recognition and organization leads to an almost unimaginable level of concentrated violence against the victims; a systematic extermination (in terms of deaths, timeframe, and geographic area) unreachable by any other prior (or subsequent) genocide.
As to the actual effects of the Holocaust and how they are significant, here is a short (and incomplete) list of how all those Holocaust deaths have impacted the world since:
Over 6 million people were murdered. In 1933 approximately 9.5 million Jews lived in Europe comprising 1.7% of the total European population. This number represents more than 60% of the World's Jewish population at that time of an estimated 15.3 million. The majority of Jews in prewar Europe lived in Eastern Europe. The largest was Poland with about 3,000,000 Jews. In Central Europe the largest Jewish population was in Germany with about 525,000 people and Western Europe the largest population was in Great Britain with 300,000. Before the Nazi seizure in 1933 Europe had a diverse set of Jewish cultures. In less than a decade two out of every three Jews would be dead. It was not only Jews but others who were seen as inferior races. The philosophy came from an false idea Germans were the superior race and meant to dominate the world. The Nazi took a combination of Norse legends and historical evidence and turned it on it's head. Himmler added superstition and occult philosophy to it making a mixture that was deadly. Had Hitler won the war he would have started to kill Christians. They all ready were rewriting The Bible before the war ended.
In Poland there were a significant number of killings after the Holocaust because some Polish nationalists believed that the Jews were Communists.
People in the baltic states that were first invaded in the summer of 1941. The disabled in Germany were the first who suffered execution for political/idealogical reasons, but this was of course not part of the Holocaust.
tworeasons we should learn about the holocaust
No... The Holocaust ended before the era called the Cold War began.
No one was killed for being Buddhist in the Holocaust.
In Poland there were a significant number of killings after the Holocaust because some Polish nationalists believed that the Jews were Communists.
What do you mean by 'justify' in the question?
People in the baltic states that were first invaded in the summer of 1941. The disabled in Germany were the first who suffered execution for political/idealogical reasons, but this was of course not part of the Holocaust.
It became the word to describe the Holocaust (before the word Holocaust).
tworeasons we should learn about the holocaust
No... The Holocaust ended before the era called the Cold War began.
By there being not as many Jews as there was before the Holocaust. If WWII had lasted for about 2 years later than when it ended, Hitler could of killed every Jew on the face of Earth.Well, you see, there was a significant lack of Jewish people when the war was through.
because they are Jews
The reasons for the Holocaust had nothing to do with religion.Please see the related questions.
No one was killed for being Buddhist in the Holocaust.
Western aristocracy is hereditary.
In Germany Nazi organizations have been banned, but for a wide range of reasons, most of them not related to the Holocaust.