More than six million Jews, including about two million children, were killed between 1933 and 1945 in Adolf Hitler's Nazi Germany, in what the world has come to know as the Holocaust.
The word, of Greek origin, roughly means death by fire, and the victims represented about two-thirds of the nine million Jews who were living in Europe at the time.
On Thursday, thousands of people paid tribute to victims of the tragedy by marching at the Auschwitz-Birkenau concentration and death camp.
A card placed on the railway tracks marks the memory of the Jews that were killed in the gas chambers. Many of them were sent to their deaths by trains that used the very same tracks.
Participants at the annual "March of the Living" event, included both young and old, as well as death camp survivors, who walked 3km from Auschwitz's "Arbeit Macht Frei" ("Work sets you free" in German) gate to the Birkenau sub-division, where most of the killings were carried out in gas chambers.
The persecution of the Jews was carried out in stages, culminating in the genocide, which is what Nazis termed the "final solution to the Jewish question", part of an overarching plan to exterminate all Jews in Europe.