It is difficult to fully understand as it deeply part of the religion and culture so they may not be able to easily explain it to you. Many political parties win elections on caste based politics, so it is large part of people's concisenesses

There are always layers within every layer whether someone is higher or lower and even within a caste it depends on genealogy(which mythical ancestor your family originates), sub varieties, socio-economic status locality, education, organizations , roles you worked at etc.

It is persistent and systemic discrimination, while things have improved in the last 70 years, there are still a lot problems. Easiest way to to figure out who someone marries especially if it is an arranged marriage