In my opinion, unconditional love has nothing to do with romance or physical expressions of affection. It is also not necessarily aimed at a particular individual, though it may be easier to experience it this way. It is a love which is not based on conditions, meaning that the particular circumstances of the love do not influence the love itself. Said another way, the particular culture, lifestyle, language, or experiences of the people involved do not contribute to the love. Rather, it is a love which is outside of facts or opinions, but is a function of something that transcends conditions.
When Charity is referenced in the King James Version of the Bible, I believe it is trying to explain this type of love. It is thought of as the holiest kind of love, the kind of love which God has for his/her creation. But I do believe that human beings have the capacity, and responsibility, to experience this love.
The closest simple analogy to unconditional love is the love that parents are inclined to have for their children. Whether the children completely screw up or hate the parents, or fulfill all their dreams, or die, or any number of possible conditions- the parents still love and care for the child. Now, this doesn’t always happen, but it can be thought of as a kind of unconditional love. However, according to my incomplete definition above, it may not be unconditional love if it depends on the fact that they have a parent-child relationship.
In other words, unconditional love should not depend on the relationship of those experiencing the love. In order to understand this, we can think about someone who loves all life, or regards all life as sacred. No matter how much people kill and torture each other, this person regards and respects them equally. This is closer to unconditional love than parents loving their children.
This is why I said earlier that unconditional love is not necessarily aimed at an individual. While we might be willing to say that we love someone unconditionally, if the love was really unconditional, it would not regard individuals as different. So, if I unconditionally love my wife, I should also unconditionally love someone who is not my wife…otherwise there is a condition that the person be married to me or be nice to me or whatever.
There is a Tibetan Buddhist practice called Tong Len which is designed to develop compassion (ie unconditional love) for others. You might find it interesting. It operates by taking natural feelings of affection and love (like for one’s spouse or family) and directing them towards strangers and enemies. The idea is to train the mind to regard enemies and family as equally worth loving.
I hope this is helpful. It’s just my opinion on a very deep matter.
I’d be interested to read was @shak has to say about this.