Humic substances are derived from Soil Organic Matter (SOM) which is playing a major role in agriculture. Quality, maturity, nativity assessment and activity of humus are determined by hydrophobic and hydrophilic (HB/HI) index, which is based on chemical composition of core structure of humic substances. Because till now there is no exact chemical formula or structure for HA and it is vary depend on source material, microbial populations, physical and chemical environment for humic substances formation, but in general it is composed ofC,H,OandN. Important functions of Humic substances in environment are, it aids in nutrient solubilization fromdrought and compacted soils, nutrient uptake by plants, heavymetals immobilization, controlling soil erosion, improvedmultiplication of essential microorganisms (EM) for agriculture. This review introduces the basic properties, composition, chemical reactivity and characterization of HS with highlighting the need of innovative research for better fundamental understanding of the mechanisms, formation transformations and application of humic substances.