This chapter distinguishes stressors, stress, and distress in the interest of bringing the use of these terms more into line with the way they are used in the stress literature and to reduce the problems of inconsistent usage prevalent in the discussion of stress in everyday life. It discusses two original stress models- biological and engineering. The chapter distinguishes varieties of stress, from life events to chronic to traumas to nonevents to daily hassles, at the individual level. It demonstrates that these distinctions are empirically supported by findings that different sources of stress have distinct impacts on mental health outcomes. The chapter discusses the issue of misconceptions about stress to argue that stress, although a general concept is a concept with theoretical and operational borders. It reviews trends in stress research, which reveal an upward trajectory in the study of all of the kinds of stress.