Primordial black holes (PBHs) are considered as a potential component of dark matter, despite the lack of direct evidence. PBHs could form from primordial density fluctuations and have mass ranges of $10^{16} - 10^{17}$ g, $10^{20} - 10^{24}$ g, and $10 - 10^3 M_{\odot}$. The last mass range is of particular interest due to recent LIGO/Virgo detections of black-hole mergers. PBHs could contribute to the formation of supermassive black holes in galactic nuclei and provide dark matter, as they are not subject to the big bang nucleosynthesis constraints. However, there are various constraints on PBHs, including evaporation, lensing, dynamical, accretion, and gravitational-wave effects. These constraints limit the possible mass windows for PBHs to provide dark matter. The mass function of PBHs can be monochromatic or extended, and the presence of non-Gaussianity and non-sphericity can affect the mass distribution. The recent detection of black-hole mergers has renewed interest in PBHs as dark matter candidates, particularly in the intermediate mass range. PBHs could also provide dark matter through their remnants or through the formation of supermassive black holes. The constraints on PBHs are complex and depend on various factors, including the mass function, the equation of state, and the redshift of the observations. The possibility of PBHs providing dark matter remains an active area of research, with ongoing studies aiming to determine the viability of this hypothesis.Primordial black holes (PBHs) are considered as a potential component of dark matter, despite the lack of direct evidence. PBHs could form from primordial density fluctuations and have mass ranges of $10^{16} - 10^{17}$ g, $10^{20} - 10^{24}$ g, and $10 - 10^3 M_{\odot}$. The last mass range is of particular interest due to recent LIGO/Virgo detections of black-hole mergers. PBHs could contribute to the formation of supermassive black holes in galactic nuclei and provide dark matter, as they are not subject to the big bang nucleosynthesis constraints. However, there are various constraints on PBHs, including evaporation, lensing, dynamical, accretion, and gravitational-wave effects. These constraints limit the possible mass windows for PBHs to provide dark matter. The mass function of PBHs can be monochromatic or extended, and the presence of non-Gaussianity and non-sphericity can affect the mass distribution. The recent detection of black-hole mergers has renewed interest in PBHs as dark matter candidates, particularly in the intermediate mass range. PBHs could also provide dark matter through their remnants or through the formation of supermassive black holes. The constraints on PBHs are complex and depend on various factors, including the mass function, the equation of state, and the redshift of the observations. The possibility of PBHs providing dark matter remains an active area of research, with ongoing studies aiming to determine the viability of this hypothesis.