>>233507
it's a color model, i.e. how pixels are represented in numbers
sRGB and Adobe RGB are colorspaces, i.e. how numbers correspond to the real color we see
in RGB color model (what PNG uses) you have values for R, G and B component
in YCbCr (what JPEG uses) it's Y, Cb, Cr
when you're converting from PNG to JPEG or other way around you have to convert from RGB to YCbCr