Examine the theoretical framework and practical implications of soil$-$structure interaction $($SSI$)$ in geotechnical engineering. Start by defining SSI and elucidating the mechanisms through which soil and structures interact, including the role of foundation types and soil properties. Discuss the various analytical approaches to modeling SSI, such as the substructure method and the continuum approach, highlighting their respective advantages and limitations$.$ Explore the factors influencing the magnitude and distribution of soil$-$structure interaction forces, including soil stiffness, foundation geometry, and loading conditions. Furthermore, analyze the significance of SSI effects on the design and performance of civil engineering structures, considering both static and dynamic loading scenarios.