It is one of those very special qualities that need humanity to possess, because unlike sympathy or even empathy, it takes willpower to be compassionate. Compassion needs contemplation, it requires selflessness, it's one of the ultimate qualities of humanity. Compassion is actually not only about being kind, it's more than that. Sometimes kindness is more bad than good, and compassion enables you to know when kindness isn't the way to go about a certain situation, and that a bit of cruelty is actually the right thing to do, because it's better for the person on the long run, so over all it's actually kinder.
Many people confuse compassion with empathy, sympathy and kindness, and this isn't right, because compassion isn't an instinct. Most of the time you actually have to beat your instinct to be truly compassionate. I mean is it easy to understand why someone was that rude to you? Isn't your instinct telling you to kick his butt for his disrespectful behavior? But you fight your instinct instead and take a moment to understand why he is acting like this, which might lead you to forgiving him, even though his behavior actually bruised your ego. There's much more to any situation than what we see, and it takes some difficult thinking to escape from our narrow perspective to see a bigger more fair picture. I believe true compassion is the way to stop your anger, beat your sadness and to end your pain, it's your way to truly forgive, heal yourself and move on.
That was what I believe true compassion is, because If you search for the meaning of the word compassion in google, you will find a different definition than what I've been explaining, which maybe the true meaning, I don't really know. I just explained a quality that I think very necessary to achieving humanity and "Compassion" is what I call it.