Structures can be grouped into different categories based on the type of forces they experience and how those forces are distributed. The main types of structures discussed are frame, arch, shell, compression, bending, tension, shear, and torsion structures. Each experiences forces in different ways - for example, tension structures experience forces that lengthen the body while shear structures experience forces that cut. Common examples like bridges, scissors, and screws illustrate how different structures withstand different types of forces.