Tribological interfaces involving contact and relative motion are everywhere in modern machinery for power transmission and function accomplishment. Automotive power generation and drivetrain systems, as well as many other motion control systems, contain various tribological interfaces. The contact of components produces stresses and the relative motion between surfaces results in rubbing. Therefore, a tribological interface is an environment where energy is consumed and materials are worn out; it is also the critical location where many failures are initiated. Designing energy-efficient and robust mechanical systems requires understanding of tribological interfaces, and the theories of contact and lubrication are two fundamental areas. This chapter summarizes fundamental theories and practices of surface, contact and lubrication analyses.