Fundamental Rights
Notwithstanding anything in this Constitution - (a) Parliament shall have, and the Legislature of a State shall not have, power to make laws with respect to matters under clause (3) of article 16, clause (3) of article 32, article 33 and article 34, and for prescribing punishment for acts declared offences under this Part; Parliament shall make such punishment-prescribing laws as soon as may be after the commencement of this Constitution; (b) any law already in force on these matters before the Constitution's commencement continues in force until altered, repealed, or amended by Parliament.
This article makes sure that only Parliament (not individual state legislatures) can make laws on certain Fundamental-Rights-related matters - like prescribing punishment for acts that Part III declares to be offences (such as untouchability under Article 17, or forced labour under Article 23) - keeping these protections uniform across the whole country rather than varying state to state.
This is why the Protection of Civil Rights Act (implementing Article 17's ban on untouchability) is a central law applicable uniformly across India, not a patchwork of different state laws with different definitions and punishments.