This article describes the genesis and composition of soil, the distinction between "pore water pressure" and inter-granular "effective stress", capillary action of fluids in the soil pore spaces, "soil classification", "seepage" and "permeability", time dependent change of volume due to squeezing water out of tiny pore spaces, also known as "consolidation", "shear strength" and stiffness of soils. The shear strength of soils is primarily derived from friction between the particles and interlocking, which are very sensitive to the effective stress. The article concludes with some examples of applications of the principles of soil mechanics such as slope stability, lateral earth pressure on retaining walls, and bearing capacity of foundations.