The caste system determined people's lives based on which social level/caste they were born in. The caste system determined people's jobs, education, etc. Once a person was born into a caste, he/she could not leave, regardless of good intentions. However, it was possible for a person to marry into a higher caste.
The caste system provided a sense of order because it strictly organized people and families. The people could not misbehave or rebel against their social statuses.