The three objects are: friends, enemies, and neutrals. The three poisons are: craving, aversion, and indifference. When you feel craving, you own it fully and wish that all beings could be free of it. When you feel aggression or indifference you do the same. In this way what usually causes suffering—what poisons us and others—becomes a seed of compassion and loving-kindness, a seed of virtue.
From Always Maintain a Joyful Mind: And Other Lojong Teachings on Awakening Compassion and Fearlessness by Pema Chödrön, pages 16-17