love: warm regard and committed care for another, shown in action.
This is the New Testament's most common word for love, and the simplest true thing to say about it is that it means "love". It does not, by itself, mean a special, purely divine, or unconditional kind of love. In ordinary Greek the same word group could describe a husband's affection, even Amnon's lust for Tamar in the Greek Old Testament, and in the Song of Songs it names the love between two human lovers. The word is plain; what fills it is the sentence it sits in.
That is why it can feel so weighty in the New Testament. Writers like Paul and John pour deep meaning into it by what they say around it. When Paul says God shows his love by Christ dying for sinners, or when John says God is love, the cross and the character of God are doing the heavy lifting, not the bare word. The famous description in First Corinthians 13 never defines love in the abstract; it shows love in action (patient, kind, not envious), so much so that you could put the name of Christ in its place and it would still read true.
So across its uses the word keeps one steady core (a settled, caring regard for another that shows itself in what you do) while context tells you who is loving whom: God toward people, people toward God, and believers toward one another. The early church also borrowed the word as the name of its shared fellowship meal, the "love feast."
The old idea that this word is a uniquely Christian term, sharply set against the Greek words for friendship and desire, has not held up. Its near twin for affection (φιλία) is used almost interchangeably with it, even of the Father's love for the Son. The lesson is not that the word is shallow, but that its depth comes from the gospel it is used to tell, not from the dictionary.