Emotion is one of the basic psychological categories. Emotions have three components (the so-called “emotional reaction triad) - they are subjective emotional experiences (e.g. joy, fear, surprise), motor symptoms (e.g. facial expressions) and accompanying physiological changes (e.g. pressure, heart pulse, etc.).
Emotions are evolutionarily older than the intellectual processes - evolutionarily older part of the brain are responsible for them. Usually they are less tractable by will than reason.