Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another’s position. Definitions of empathy encompass a broad range of emotional states. Types of empathy include cognitive empathy, emotional empathy, and somatic empathy.
The English word empathy is derived from the Ancient Greek word εμπάθεια (empatheia, meaning “physical affection or passion”). This, in turn, comes from εν (en, “in, at”) and πάθος (pathos, “passion” or “suffering”). The term was adapted by Hermann Lotze and Robert Vischer to create the German word Einfühlung (“feeling into”), which was translated by Edward B. Titchener into the English word “empathy”.
Compassion and sympathy are terms associated with empathy. Definitions vary, contributing to the challenge of defining empathy. Compassion is often defined as an emotion we feel when others are in need, which motivates us to help them. Sympathy is a feeling of care and understanding for someone in need. Some include in sympathy an empathic concern, a feeling of concern for another, in which some scholars include the wish to see them better off or happier.
Empathy is distinct also from pity and emotional contagion. Pity is a feeling that one feels towards others that might be in trouble or in need of help as they cannot fix their problems themselves, often described as “feeling sorry” for someone. Emotional contagion is when a person (especially an infant or a member of a mob) imitatively “catches” the emotions that others are showing without necessarily recognizing this is happening.
The human capacity to recognize the bodily feelings of another is related to one’s imitative capacities, and seems to be grounded in an innate capacity to associate the bodily movements and facial expressions one sees in another with the proprioceptive feelings of producing those corresponding movements or expressions oneself. Humans seem to make the same immediate connection between the tone of voice and other vocal expressions and inner feeling.
In the field of positive psychology, empathy has also been compared with altruism and egotism. Altruism is behavior that is aimed at benefitting another person, while egotism is a behavior that is acted out for personal gain. Sometimes, when someone is feeling empathetic towards another person, acts of altruism occur. However, many question whether or not these acts of altruism are motivated by egotistical gains. According to positive psychologists, people can be adequately moved by their empathies to be altruistic, and there are others who consider the wrong moral leaning perspectives and having empathy can lead to polarization, ignite violence and motivate dysfunctional behavior in relationships.
Heinz Kohut is the main introducer of the principle of empathy in psychoanalysis. His principle applies to the method of gathering unconscious material. The possibility of not applying the principle is granted in the cure, for instance when you must reckon with another principle, that of reality.
In evolutionary psychology, attempts at explaining pro-social behavior often mention the presence of empathy in the individual as a possible variable. While exact motives behind complex social behaviors are difficult to distinguish, the “ability to put oneself in the shoes of another person and experience events and emotions the way that person experienced them” is the definitive factor for truly altruistic behavior according to Batson’s empathy-altruism hypothesis. If empathy is not felt, social exchange (what’s in it for me?) supersedes pure altruism, but if empathy is felt, an individual will help by actions or by word, regardless of whether it is in their self-interest to do so and even if the costs outweigh potential rewards.

Source: Wikipedia