Soil mechanics is a branch of mechanics which deals with the action of forces on soil and with the flow of water in soil. Soil engineering in an applied science dealing with applications of principles of soil mechanics to practical problems. It includes site investigations, design and construction of foundations, earth retaining structures, and earth structures. Geotechnical engineering is a broader term which includes soil engineering, rock mechanics, and geology. Soil structure is an important factor which influences many soil properties, such as permeability, compressibility, and shear strength, and so on. This chapter explores the types of soil structures. Consistency of soil is meant for the relative ease with which soil can be deformed. Soil classification is the arrangement of soils into different groups such that the soils in a particular group have similar behaviour.