Sudras are the last of the four Varnas, the other three being Brahmin , Ksatriya and Vaisya . Sudras are the working class and thus the breadwinner of the society. Major chunk of the society is formed by Sudras.

Slavery is not practiced in India and Sudras are not slaves. The Western scholars who come from countries which practice slavery depict Sudras as slave is not true. They were the working class supporting their respective masters in other three castes. They supported priest in some priestly works, worked in army in lower ranks and done all the manual work in agriculture and industry. They are of course not the elite citizens, but they have their respect as good citizen and workforce.

The great scholars born to poor servants were not considered as Sudras. Vyasa was son of fisher women; He compiled the Four Vedic Samhitas. Upanisadic sage Sathyakama was a son of a servent maid. He was called a Brahmin by his teacher. B.G. Says the four casts is created by the Lord Himself according to the qualities and duty (guna karma) of each person and address Arjuna as Brahmana and Ksatriya according to the circumstances.

It is true that there some references which denigrate the status of Sudras and consider them as third class people exist in Puranas and Darmasastras. But the general attitude of Veda, Purana and Darmasastra is not in support of this attitude. So we can only say, those stray verses can be either interpolated or unfortunate references and thus we should not consider them as authentic or worth to follow.

Untouchablility, restriction in using public facilities and such social vices were practiced against Sudras during last few centuries. The foreign rulers who ruled during the last 8 centuries only tried their best to divide the gap between different classes in Hindu society. It is by the effort of the Bhakti cult sages this evil was brought down to some extent. During 20th century great movement lead by Gandhiji, Dr. Ambedkar, and many other regional leadership started against the evil practice and that brought revolutionary changes in Hindu society.