Efficient thermal management is a critical requirement in modern electronic systems due to continuous miniaturization and increased power density. Pin-fin heat sinks have emerged as an effective cooling solution because of their high surface area, enhanced mixing characteristics, and suitability for multidirectional airflow. This review paper presents a comprehensive analysis of heat transfer characteristics of pin-fin heat sinks operating under natural and forced convection conditions. The study examines geometrical configurations, fin materials, fin spacing, fin height, arrangement patterns (inline and staggered), and airflow parameters influencing thermal performance. Under natural convection, buoyancy-driven flow significantly affects thermal resistance and temperature distribution, while forced convection improves heat dissipation through enhanced turbulence and higher heat transfer coefficients. Experimental, numerical, and analytical investigations reported in the literature are critically reviewed to compare thermal resistance, Nusselt number variation, pressure drop, and overall efficiency. The influence of Reynolds number, Prandtl number, and fin geometry on heat transfer enhancement is also discussed. Furthermore, advancements such as perforated fins, micro pin-fins, and optimized geometries using computational fluid dynamics (CFD) are evaluated. The review identifies research gaps related to hybrid cooling techniques, optimization under low airflow conditions, and material innovation. The findings provide a consolidated understanding of performance parameters and design considerations for improved thermal management in electronic cooling applications. This review aims to serve as a reference framework for researchers and engineers working on compact and high-performance heat sink design.