From C.S. Lewis via Fr. Longenecker:
Standing on My Head:
"Affection is the natural love we have for our families. This is the love for our mother our father and the general love we have of our tribe, our nation, our people, our country.
Friendship is the love we have with another with whom we share an outside interest. It is the love of the soldier, the team mate and the member of a club.
Eros is romantic love. A part of eros is sexual attraction. This natural love still has an element of self interest. We love because we are loved, and we are attracted through the natural desire for sexual relations and to procreate.
Charity is the the highest love. It is the unconditional love of another for their own sake. It desires the good of the other person even at our expense. This is the love God has for us and the love we should have (through grace) for Him and for others."