Metta (lovingkindness) = friendly kindness that wishes self and others well.
Karuna (compassion) = the trembling heart that responds to pain and suffering.
Mudita (sympathetic joy) = appreciating the good in the world, enjoying others' happiness and success.
Upeksha (equanimity) = balance and clarity in the midst of experience.
The four immeasurables are alternately aspirations, intentions, attitudes, and feelings.
They do not depend on outer circumstances nor on one's inner state.
They lead to insight -- to knowing how things are.
They lead to the ability to be present and responsive.