Stellar black holes and compact stellar remnants

The recent observations of gravitational waves (GWs) by the LIGO-Virgo-Kagra collaboration (LVK) have provided a new opportunity for studying our Universe. By detecting several merging events of black holes (BHs), the LVK has spurred the astronomical community to improve theoretical models of single, binary, and multiple star evolution in order to better understand the formation of black hole binary (BBH) systems and interpret their observed properties. The final BBH system configuration before the merger depends on several processes, including those related to the evolution of the inner stellar structure and those due to the interaction with the companion and the environment (such as in stellar clusters). This chapter provides a summary of the formation scenarios of stellar BHs in single, binary, and multiple systems. We review all the important physical processes that affect the formation of BHs and discuss the methodologies used to detect these elusive objects and constrain their properties.