One of my college professors told us a definition of love that I've never forgotten. "When the happiness and well-being of another is essential to one's own happiness and well-being, a state of love exists."
Of course romantic feelings and physical attraction are important because the human race would have vanished long ago if people didn't reproduce.
And sometimes people must do things that make someone they love unhappy, such as parents refusing to give children things they want, or even punishing them. But if those acts are done for the long-term happiness and well-being of the children they are expressions of love.
But on Valentine's Day it's fun to show love by making people we care about happy right now. How will you show your love to others?