It puts limits to the legislative powers of the Parliament and stops it from turning this limited power into absolute power. The elements of 'Basic Structure' of the Constitution aren't defined by the Supreme Court but they are implicit in various judgement by the SC.

The constitution validity of First Amendment Act, 1951, which curtailed the Right to Property was challenged.

SC ruled that the definition of law as mentioned in Article 13 of Indian Constitution doesn't include Amendment Bills and thus, Parliament can abrogate Fundamental Rights by passing Amendment Bills and they'll be outside the purview of Judicial review.

The constitutional validity of Seventh Amendment Act, 1964 was challenged in the SC as it inserted certain State Acts in 9th Schedule.

SC ruled that Amendment Acts come under the purview of Article 13 and hence, they can be put under Judicial Review. Also, SC ruled that FR are transcendental and immutable and can't be bridged away by an Amendment Act.

Parliament reacted to the ruling of Golak Nath Case, 1967 by passing 24th Constitutional Amendment Act, 1971. It amended Article 13 and Article 368 and gave Parliament infinite powers to amend constitution and abrogate any FRs.

SC overruled it's verdict in Golak Nath Case, 1967 and upheld the validity of 24th CAA, 1971. It stated that Parliament can bridge away FRs of the citizens by passing amendment acts but it can't alter the "Basic Structure" of the constitution.

Thus, the constitutional doctrine of Basic Structure was conceived in Kesvananda Bharti Case, 1973

SC declared the 39th Constitutional Amendment Act as unconstitutional as it had put the matters related to election disputes of PM and LS Speaker, outside the purview of every court.

SC ruled that 'Judicial Review' forms the 'Basic Structure' of the constitutional

This parliamentary act reacted to the judicial creation of Basic Structure doctrine.

The act amended Article 368 and gave Parliament absolute powers wrt amending the constitution and abrogating FRs of the citizens. Also, it included that such amendments can't be questioned in any court of law.

SC declared 42nd CAA, 1976 unconstitutional as it excluded 'Judicial review' which was the part of basic structure of the constitution.

SC adhered to the guidelines set under the Basic Structure Doctrine and ruled that it would apply to constitutional amendments enacted after April 24, 1973.