This paper presents new constraints on the fraction of the Universe that could be composed of primordial black holes (PBHs) in the mass range $10^9 - 10^{17}$ grams. These constraints are derived from the effects of PBH evaporation on big bang nucleosynthesis (BBN) and the extragalactic gamma-ray background. The authors include the effects of quark and gluon emission by PBHs and account for the latest observational developments. They show that the constraints from BBN and the gamma-ray background are stronger than other constraints, except for a small range $10^{13}-10^{14}$ grams, where the damping of cosmic microwave background anisotropies dominates. The paper also reviews the gravitational and astrophysical effects of non-evaporating PBHs over a broader mass range $1-10^{50}$ grams. The paper discusses the formation of PBHs in the early Universe, their mass range, and the implications of their evaporation. It also reviews the effects of PBHs on BBN and the gamma-ray background, and the constraints on their mass spectrum. The authors update the constraints on the fraction of the Universe that could be composed of PBHs, taking into account the latest observational and theoretical developments. They also discuss the implications of PBHs for dark matter and the potential for PBHs to be the source of dark matter. The paper concludes with a summary of the most important limits on PBHs in different mass ranges.This paper presents new constraints on the fraction of the Universe that could be composed of primordial black holes (PBHs) in the mass range $10^9 - 10^{17}$ grams. These constraints are derived from the effects of PBH evaporation on big bang nucleosynthesis (BBN) and the extragalactic gamma-ray background. The authors include the effects of quark and gluon emission by PBHs and account for the latest observational developments. They show that the constraints from BBN and the gamma-ray background are stronger than other constraints, except for a small range $10^{13}-10^{14}$ grams, where the damping of cosmic microwave background anisotropies dominates. The paper also reviews the gravitational and astrophysical effects of non-evaporating PBHs over a broader mass range $1-10^{50}$ grams. The paper discusses the formation of PBHs in the early Universe, their mass range, and the implications of their evaporation. It also reviews the effects of PBHs on BBN and the gamma-ray background, and the constraints on their mass spectrum. The authors update the constraints on the fraction of the Universe that could be composed of PBHs, taking into account the latest observational and theoretical developments. They also discuss the implications of PBHs for dark matter and the potential for PBHs to be the source of dark matter. The paper concludes with a summary of the most important limits on PBHs in different mass ranges.