We all know and experience physical and mental pain

The Buddha was very sophisticated when teaching about compassion, and about everything. He taught there are different gradations of suffering, or dukkha. Superficially we all know and experience physical and mental pain. A little hidden is change. No more chocolate cookies! Or waking up with sunburn after the pleasure of laying out at the beach. More hidden yet is the foundation for all our suffering. It mistakes who we are and what the world is, almost like we are hallucinating! We call this distorted ignorance. Because we are so habituated to believing that things exist on their own, objectively, this ignorance is hard to recognize. Once we do, we meditate on its opposite. This process leads us to understanding and experiencing reality correctly. In Sanskrit this is called śūnyatā. In English, emptiness. Emptiness overturns all suffering. Coupled with Bodhicitta, it leads directly to enlightenment.