Positive affect and emotion have become major topics in behavioral science, of growing importance in basic and applied research. A broad review of the literature reveals multiple, theoretically distinct constructs associated with the terms ‘positive affect’ and ‘positive emotion,’ sometimes conflated across this body of work. This article differentiates three primary constructs — subjectively pleasant affect; approach or appetitive motivation; and emotion states evoked by opportunities and rewards in the environment — and summarizes the major theoretical perspective with which each is intertwined. While these versions of positivity often coincide in lived emotional experience, we highlight examples of divergence, and discuss dynamic ways in which they influence each other. Distinct cognitive, physiological, and behavioral mechanisms by which each version of positivity may produce downstream effects are discussed, as is the importance of selecting and operationalizing the target construct with care in both basic affective science and translational research.