Soils are classified into three types based on their formation process: sedimentary, residual, and fill. The document categorizes specific soils, identifying weathered granite and laterite as residual soils, glacial till and loess as sedimentary, and constructed levees and highway pavement subgrade as fill. It also notes that alluvium and seabed clays are classified as residual soils, while soils in the riverbed of the Connecticut River are sedimentary.