Altruism and Prosocial Behavior

Examine the concept of altruism and altruistic behavior. What does it mean for someone to behave altruistically? What is gained from this action, and how does it differ from egoistic behavior? What are some reasons why people would want to help one another, without regard for personal gain or benefit?  In addition, explain the bystander effect.  If we all have a genuine desire to help one another, why is the effect so common?  How can we prevent it from occurring?