What produces emotions? Why do we have emotions? How do we have emotions? Why do emotional states feel like something? This book seeks explanations of emotion by considering these questions. Emotion continues to be a topic of enormous scientific interest. 'Emotion Explained' describes the nature, functions, and brain mechanisms that underlie both emotion and motivation. However it goes beyond examining brain mechanisms of emotion, by proposing a theory of what emotions are, and an evolutionary, Darwinian, theory of the adaptive value of emotion. It also shows that there is a clear relationship between motivation and emotion. The book also examines how cognitive states can modulate emotions, and in turn, how emotions can influence cognitive states. It considers the role of sexual selection in the evolution of affective behaviour. It also examines emotion and decision making, with links to the burgeoning field of neuroeconomics. The book is also unique in considering emotion at several levels - the neurophysiological, neuroimaging, neuropsychological, behavioural, and computational neuroscience levels.