From the Wikipedia:
"Agapē (IPA: /ˈægəpiː/) (Gk. αγάπη [aˈɣa.pi]), is one of several Greek words translated into English as love. The word has been used in different ways by a variety of contemporary and ancient sources, including Biblical authors. Many have thought that this word represents divine, unconditional, self-sacrificing, active, volitional, and thoughtful love. Greek philosophers at the time of Plato and other ancient authors have used forms of the word to denote love of a spouse or family, or affection for a particular activity, in contrast to philia—an affection that could denote either brotherhood or generally non-sexual affection, and eros, an affection of a sexual nature. The term 'agape' is rarely used in ancient manuscripts, but was used by the early Christians to refer to the self-sacrificing love of God for humanity, which they were committed to reciprocating and practicing towards God and among one another (also see kenosis).
Agape has been expounded on by many Christian writers in a specifically Christian context. Thomas Jay Oord has defined agape as "an intentional response to promote well-being when responding to that which has generated ill-being." (http://en.wikipedia.org/wiki/Agape)