The Guardian reports:
The 78-year-old pontiff devoted much of the first half of his treatise to the relationship between Eros - erotic love - and Agape, the Greek word for unconditional and selfless love...
The encyclical says both forms are interrelated: "The more the two, in their different aspects, find a proper unity in the one reality of love, the more the true nature of love in general is realised."
Read the Guardian story, or the actual encyclical.