What is love?
This is a first century Christian description of love from a converted Jewish Rabbi.
“(4) Love is patient and kind. Love is not jealous or boastful or proud (5) or rude. It does not demand its own way. It is not irritable, and it keeps no record of being wronged. (6) It does not rejoice about injustice but rejoices whenever the truth wins out. (7) Love never gives up, never loses faith, is always hopeful, and endures through every circumstance.” [1 Corinthians 13:4-7 NLT]
The Greeks had several words for love
Eros – A love for the beauty of something or the quality of excellence.
Phaedrus 249E: “he who loves the beautiful is called a lover because he partakes of it.” Plato, Trans. Jowett
Phila – Friendship – “things that cause friendship are: doing kindnesses; doing them unasked; and not proclaiming the fact when they are done” (Aristotle; Rhetoric, II. 4, trans. Rhys Roberts).
Storge – Unconditional love of the family.
Agape – Giving unconditional family love to people who are not family
“To love is to will the good of the other.”
[Thomas Aquinas], Summa Theologica (1265–1274), II-II, q. 26, art. 6
John, the best friend of Jesus of Nazareth said:
“(8) But anyone who does not love does not know God, for God is love. … (16) We know how much God loves us, and we have put our trust in his love. God is love, and all who live in love live in God, and God lives in them.” [1 John 4:8, 16 NLT]
Jesus of Nazareth, believed to be the Messiah by Christians said concerning love:
“(43) “You have heard the law that says, ‘Love your neighbor’ and hate your enemy. (44) But I say, love your enemies! Pray for those who persecute you! (45) In that way, you will be acting as true children of your Father in heaven. For he gives his sunlight to both the evil and the good, and he sends rain on the just and the unjust alike. (46) If you love only those who love you, what reward is there for that? Even corrupt tax collectors do that much. (47) If you are kind only to your friends, how are you different from anyone else? Even pagans do that. (48) But you are to be perfect, even as your Father in heaven is perfect.” [Matthew 5:43-48 NLT]
in 1977 using factor analysis of 1500 items related to love, John Lee categorized 6 major types of love:
- Eros Love – erotic desire for an idealized other
- Ludus Love – playful or game-like love
- Storge Love – slowly developing attachment
- Mania Love – obsessive and Jealous love
- Pragma Love – practical love
- Agape Love – altruistic Love (Selfless devotion)
It would seem right to add to this “Philos” love so that the area of friendship is covered effectively
So what is love? Clearly it is a word used to explain a wide range of emotions and actions. Clearly there are many different shades of love and applications. One thing that would be important is when we use the word love that we try to describe or define exactly what shade or flavor of love we have in mind.
Dr. Thomas Aquinas seems to have hit upon a key element that should be part of all the different types of love, which would to will the good of the other. Jesus the Messiah summarized the heart of this saying
“(13) There is no greater love than to lay down one’s life for one’s friends.” [John 15:13 NLT]
The idea of God being love in the Christian tradition is seen that in the person of Jesus of Nazareth the Messiah, God laid down his life to give life to others. This is the heart of the Christian story that has touched so many lives and motivated so many to imitate such love in sacrificial service to others.
On example of this in modern times can be found in Christiana Noble and her work with orphaned children in Vietnam ( https://www.cncf.org/ ). I would urge you to watch the movie “Noble” about this amazing woman and how the influence of God in her life motivated her to reach out to the children that are hurting. (https://www.rottentomatoes.com/m/noble_2014/ )
To live a successful life is to learn to love well. Failing to love well is true failure in life. Love is the most important of all the virtues. To the degree we attain love we have fulfilled our potential for having a good and useful life. Therefore, striving to better understand love would seem to be an essential aspect of learning to live effectively. 
See this excellent discussion. https://ayosage.wordpress.com/2012/03/14/the-7-types-of-love-revised/