Michael K. answered 08/05/19
Retired Nuclear Engineer and software tester.
Planck's curve is generated by application of Planck's law to give the power density of different frequencies of black body radiation for a give temperature. These results agreed with observation. Planck's curve was the first mathematical model to use Planck's concept of quantization to accurately describe real physical systems. Further development Planck's concept of quantization would lead to quantum mechanics.