Hexagonal boron nitride (h-BN) stands out for its unique properties and structural similarities to carbon, making it valuable across fields such as optoelectronics, nanophotonics, catalysis, and industrial applications. This review paper explores the history, fundamental properties, classification, synthesis, and broad applications of hBN. h-BN produced via the exfoliation and chemical vapor deposition (CVD) methods exhibit high thermal stability, chemical resistance, and exceptional mechanical properties, which make it suitable for various industrial and technological uses. In water treatment, h-BN contributes to reverse osmosis (RO) membranes by enhancing stability and water flux, making it effective in desalination, while its high surface area enables efficient adsorption of contaminants. Additionally, the application of h-BN in adsorbing dyes, oils, and metal ions from wastewater underscores its role in water treatment and environmental management. Insights from molecular dynamics and density functional theory (DFT) studies offer a deeper understanding of h-BN's versatility, and ongoing research reveals its expanding potential in driving advancements across multiple sectors.