Substantive due process refers to the concept that certain rights are so fundamental that the government cannot infringe upon them, even through the normal democratic processes. It emphasizes that laws and government actions must be fair, reasonable, and just, and cannot arbitrarily deprive individuals of their life, liberty, or property. It ensures that individuals are given a fair and meaningful opportunity to be heard and have their rights protected by the legal system. Ultimately, substantive due process serves to limit the power of the government and protect individual rights from arbitrary government actions.