What is a Communist? Why would Anja be helping them, and why would this make Vladek angry?

There are many signs of a growing conflict between these classes. Communism, a theory that supports the idea of a classless state in which the common people control the means of production (factories, tools, materials, etc), has gained a foothold in the country, and Vladek returns from the sanitarium with Anja to find that his factory has been robbed. Vladek dislikes communism because the system would take away his social status as well as all the profit he worked so hard to build his factory for.