Actually, the Soviet Union was a "communist" nation. Communism tries to create a society based on equatlity for everyone and a government that will take care of a persons' physical needs provided they give up some of their freedoms. Also, under communism, most everything is owned and operated by "the state" and everyone and everything should be working toward the good of the country.
Socialism on the other hand, bases their ideals on creating classes in society. Nazi Germany had a "socialist" government and were able to say that this group is at the top, while this group is at the bottem and expendable and various stations in between. Under Socialism, all major industries are controlled by the govenment, but private ownership of smaller businesses is allowed.