Abundance refers to the total number of primordial black holes (PBHs) present, while the mass spectrum describes the distribution of these black holes across different mass ranges. The calculation of abundance involves integrating the Gaussian probability density function, which may not directly yield a simple count of black holes. Instead, this integration provides a mass density or a statistical representation of their distribution. Additional context is necessary for a more precise understanding of how these concepts apply to specific scenarios in PBH research.
