1) Caste system of India was based on the occupation of people and it was termed as varna system. As per this system, Kshatriyas and Brahmanas were considered as upper castes while Vaishyas and Shudras were regarded as lower castes
2) This economic status caused inequalities among other castes of the people. The life of Shudras or untouchables were very worst. They were not allowed to enter temples, has to do menial jobs, they were not allowed to enter the region of upper castes etc. Their life was like that of slaves. They have to serve upper caste sections of society like Kshatriyas, Brahmanas etc
3) During the ancient times, untouchables were oppressed of their privileges like education, freedom of movement within the territory, etc by upper caste sections of society