How were the people in the Holocaust transported to the death camps?

Through tightly packed cattle cars, with one small window (packed in like sardines)
The most common means of transportation for Jewish and many other prisoners in WW2 was by rail. The Jews were transported in enclosed boxcar by train, and it was dark and packed full. They were not fed at all during the journey and there were no lavatory facitilies. Many died due to starvation, thirst and weather conditions.