The aim of Tribology is the minimisation of friction and wear occurring in nearly all machine elements with contact surfaces under relative motion. The course “Tribology” is offered at RWTH Aachen University for advanced studies in mechanical engineering and master students. The lecture documentation reviews the basics of Tribology. It deals with the interactions between the contacting surfaces (e.g. contact processes, friction and wear mechanisms). The properties of the contacting bodies as well as the intermediate medium are presented and the basics of fluid dynamics are explained. On this basis, different machine elements (plain bearings, gear wheels, rolling bearings and seals) are discussed concerning tribological interactions. Different influences on the performance of the machine elements are presented in consideration of the basics of Tribology.