The application-oriented book introduces the relationship between contact mechanics and friction, thereby enabling a deeper understanding of tribology. It addresses the closely interconnected phenomena of contact, adhesion, capillary forces, friction, lubrication, and wear from a unified perspective. The author discusses (1) methods for rough estimation of tribological quantities, (2) methods for analytical calculation in a minimally required scope, and (3) the transition to numerical simulation methods. This provides a cohesive view of tribological processes across different scales (from nanotribology to earthquake research). It also covers system dynamic aspects of tribological systems, such as squeaking and its mitigation, as well as other types of instabilities and pattern formation. Exercises with worked-out solutions are included.