The current state of research on high-intensity laser fields and their interaction with charged particles is reviewed. Data on petawatt-class laser facilities are presented, and advanced methods for characterizing ultra-intense laser pulses are discussed. Effects that occur in the interaction of such pulses with matter in the regime dominated by radiation friction are considered. Methods applied to describe nonlinear quantumelectrodynamic processes, including higher-order effects, are described in detail. Some theoretical results and concepts are criticized, including the predicted influence of strong laser fields on decays of nuclei and elementary particles and the concept of Unruh radiation.