This is a rather vague question -- the link I have added here is to a 16 page pdf that explains the National Population Policy of 2000. It is hard to know which aspects of the policy you want explained.
Basically speaking, the National Population Policy is aimed at reducing the growth of India's population. Unlike China's population policy, however, India's is not coercive. Instead, it is based on the idea of persuading and encouraging people to have fewer children. For example, there is a strong emphasis on family planning and contraceptives. There is also an emphasis on education to get more people to voluntarily reduce the number of children they are having.
So the basic explanation of this policy is that India wishes to reduce the growth of its population but, very importantly, wishes to do so through education and voluntary action rather than through coercion the way China has.