Primordial black holes (PBHs) are a potential dark matter (DM) candidate, formed from density fluctuations in the early Universe. Unlike traditional DM candidates like WIMPs or axions, PBHs are not new particles but can be formed in the right abundance to constitute DM. Their formation is linked to 'Beyond the Standard Model' physics, such as inflation. The discovery of gravitational waves from black hole mergers by LIGO-Virgo has reignited interest in PBHs as DM. PBHs can form during radiation domination, and their abundance depends on the amplitude of primordial density perturbations. Current observational constraints suggest that PBHs with masses around $10^{17}$ to $10^{22}$ grams (asteroid mass window) could constitute all DM, while smaller PBHs are ruled out. Future observations, including gamma-ray telescopes and microlensing surveys, may provide tighter constraints. Open questions include how to detect PBHs in the asteroid mass window, the probability distribution of density perturbations in ultra-slow-roll inflation, and the clustering of PBHs on subgalactic scales. PBHs could have significant implications for the distribution of matter in the Universe and the observed gravitational wave background. The field is rapidly evolving, with ongoing research into their formation, abundance, and observational signatures.Primordial black holes (PBHs) are a potential dark matter (DM) candidate, formed from density fluctuations in the early Universe. Unlike traditional DM candidates like WIMPs or axions, PBHs are not new particles but can be formed in the right abundance to constitute DM. Their formation is linked to 'Beyond the Standard Model' physics, such as inflation. The discovery of gravitational waves from black hole mergers by LIGO-Virgo has reignited interest in PBHs as DM. PBHs can form during radiation domination, and their abundance depends on the amplitude of primordial density perturbations. Current observational constraints suggest that PBHs with masses around $10^{17}$ to $10^{22}$ grams (asteroid mass window) could constitute all DM, while smaller PBHs are ruled out. Future observations, including gamma-ray telescopes and microlensing surveys, may provide tighter constraints. Open questions include how to detect PBHs in the asteroid mass window, the probability distribution of density perturbations in ultra-slow-roll inflation, and the clustering of PBHs on subgalactic scales. PBHs could have significant implications for the distribution of matter in the Universe and the observed gravitational wave background. The field is rapidly evolving, with ongoing research into their formation, abundance, and observational signatures.