Explanation:

1. Preamble is a part of the Constitution. But one cannot go to court to get it enforced, i.e. non-justiciable.
2. The State cannot do something just because it is mentioned in the Preamble, nor it is restrained to do something just because the Preamble disallows it.
3. Preamble is a key to the minds of our Constitution makers. Hence, it can be useful in interpreting a  a provision of Constitution in times of ambiguity.
4. Preamble can be amended by Parliament using its amendment powers as per article 368. We note here that preamble has been amended only once so far through the 42nd Constitution Amendment Act 1976. The words Secular, Socialist and Integrity were added to the constitution. Berubari Union Case (1960) ,SC declared that Preamble was a part of constitution, so it is not a recent declaration.