Primordial Black Holes (PBHs) are a potential candidate for dark matter, formed from overdensities in the early universe. They are cold, non-baryonic, and stable, making them a viable dark matter candidate. The discovery of gravitational waves from binary black hole mergers by LIGO-Virgo has renewed interest in PBH dark matter. This review covers the formation of PBHs, observational probes of their abundance, and key open questions in the field. PBHs can form from large density perturbations during radiation domination, with a critical density contrast above which they collapse into black holes. The mass and abundance of PBHs depend on the amplitude of these perturbations, which must be significantly larger on small scales compared to cosmological scales. Inflationary models can generate such large perturbations, but they are not generic. Observational constraints on PBHs include evaporation, microlensing, gravitational waves, accretion, and dynamical effects. Current constraints suggest that planetary, solar, and multi-solar mass PBHs cannot make up all dark matter, but lighter asteroid mass PBHs could. Future observations, such as those from MeV gamma-ray telescopes, will tighten these constraints. Key open questions include how to probe asteroid mass PBHs, the probability distribution of density perturbations produced by ultra-slow-roll inflation, and the clustering of PBHs on subgalactic scales. These questions are crucial for understanding the role of PBHs in dark matter and their implications for astrophysical phenomena.Primordial Black Holes (PBHs) are a potential candidate for dark matter, formed from overdensities in the early universe. They are cold, non-baryonic, and stable, making them a viable dark matter candidate. The discovery of gravitational waves from binary black hole mergers by LIGO-Virgo has renewed interest in PBH dark matter. This review covers the formation of PBHs, observational probes of their abundance, and key open questions in the field. PBHs can form from large density perturbations during radiation domination, with a critical density contrast above which they collapse into black holes. The mass and abundance of PBHs depend on the amplitude of these perturbations, which must be significantly larger on small scales compared to cosmological scales. Inflationary models can generate such large perturbations, but they are not generic. Observational constraints on PBHs include evaporation, microlensing, gravitational waves, accretion, and dynamical effects. Current constraints suggest that planetary, solar, and multi-solar mass PBHs cannot make up all dark matter, but lighter asteroid mass PBHs could. Future observations, such as those from MeV gamma-ray telescopes, will tighten these constraints. Key open questions include how to probe asteroid mass PBHs, the probability distribution of density perturbations produced by ultra-slow-roll inflation, and the clustering of PBHs on subgalactic scales. These questions are crucial for understanding the role of PBHs in dark matter and their implications for astrophysical phenomena.