There are a lot of differences between empathy and sympathy.  Sympathy is Feeling bad for someone elses misfortune, this deals a lot with emotion.  Actions often associated with sympathy are comforting someone or offering condolences.  Empathy is the intellectual identification with an experience of thoughts or feelings of others.  Empathy is a critical thinking skill.  Empathy is an essential tool for historians because in order to understand why something happened or why someone made the decision they did you have to put yourself in to their shoes and think about what different types of people might have done in that situation.
                                                                                                                              Wyatt