Friction, lubrication, and wear have a strong influence on the performance and behavior of mechanical systems. This paper deals with different friction models for sliding contacts running under different conditions. The models presented are suited to different situations, depending on the type of contact, running conditions, and the behavior of interest. The models will be discussed from simulation and tribological points of view. The different types of friction models considered are: •friction models for transient sliding under dry, boundary and mixed lubrication conditions,•friction models for micro-displacements of engineering surfaces subjected to transient sliding,•friction models often used in the simulation and control of technical systems,•combined friction models that represent physical behaviors fairly well but are also suitable for use in simulating systems,•friction models that take into account the stochastic nature of interacting surface asperities.