Why Are People Influenced to Help Others Even When They Are on the Other Side of the World?

What makes people (like people from Peace Corps) want to help the less fortunate? What motivates them to do so? Are there any specific people or organizations that are similar to Peace Corps or at least influential organizations/ people?

Suggestion:

Because people have a moral conscience, and when its clear that people in countries far away that have a less stable infrastructure, are poverty stricken, and suffer from social deprivation, hunger, disease and are unable to rebuild their countries efficiently after natural disasters and other crisis', then some people are going to be motivated enough to donate money, travel over their to offer support and try and aid these people.