As Kalu Rinpoche (d. 1989) said in Luminous Mind:
Compassion, Kindness, and Love together form the essential Mahayana
attitude. Their foundation is a non self-cherishing frame of mind oriented
towards others, aspiring to the well-being and happiness of all other beings,
whether human or non-human, friends or enemies.
It arises when we perceive the suffering of others. It is the first kind of compassion to arise, and causes us to strive deeply to do everything we can to help all those who suffer. It emerges when we perceive the pain and sufferings or others.
This form of compassion is marked by our no longer being able to remain unmoved by the suffering of beings and by aspiring to do everything possible to help alleviate their suffering.
It arises when we have a genuine experience of the power of ignorance; when we actually perceive how beings create their own suffering. This compassion occurs when we really see how others strive to be happy and avoid suffering but how, not understanding the causes of happiness nor the means of avoiding suffering, they produce more causes of suffering and have no idea how to cultivate the causes of happiness. They are blinded by their ignorance, their motivations and actions contradict one another.
Through understanding the illusory nature of reality, genuine perception of
this situation beings forth this 2nd type of compassion, which is more intense
and profound than the1st kind.
It retains no notion of subject, object, or intention. It is the ultimate form of a Buddha's or great Bodhisattva's compassion and depends upon the realization of emptiness. There is no longer any reference to a 'me' or 'other'.
This compassion opens naturally and spontaneous.
It is important to be familiar with these 3 types of compassion; to
understand their order, and to being to work at the first level, which is the
most accessible to us.
Like all beings, they have been our mothers and fathers in past lives; each has his or her suffering. Their present situation, their wealth or power, results from previous positive karma, but they are no less marked by a strong sense of ego and by many afflictions.