Jews resisted the Nazis in different ways: physically, spiritually and morally.
In many ghettos and camps, there was armed resistance. The most famous example of this took place in April-May 1943 when the few remaining Jews from the Warsaw Ghetto held German troops at bay for almost a month. Other Jews joined partisan and other resistance groups across occupied Europe to fight against the Germans.
There was also spiritual resistance. Jews in the ghettos and camps refused to let the Nazis dehumanize them, that is to deprive them of the qualities and characteristics that made them feel civilized. Thus, when the German authorities forbade Jews in the ghettos from educating their children, they held secret classes. Jews also organized clandestine prayer services to observe Shabbat, the Jewish High Holy Days, and other Jewish religious festivals.
Finally, Jews in the ghettos and camps supported one another morally and emotionally, even in the gas chambers. There are many accounts of how Jews sang national and religious songs while being led to their deaths, and of parents comforting children on the edge of the shooting pits.