I sometimes think of the Theravada concept of Sati as an “extra layer” of consciousness or awareness. It’s the difference between being a thought and understanding that you are experiencing a thought. Being angry vs. experiencing anger. The difference seems to be that you do not feel completely identified with a mental state. There is a distance between “you” and what you are experiencing.
The Theravada tradition distinguishes between two primary forms of meditation. In one of the primary forms – Mindfulness Meditation – one explicitly works on the development of Sati/Mindfulness. In the other primary form – Jhana Meditation – one develops the skill of concentration.
Not all Buddhist meditative traditions recognize this distinction in meditative practice. For instance, Zen meditative practice is typically much more simplified. Just sit and follow your breath. Or even “just sit.” Let whatever unfolds unfold.
I believe that during my practice of Centering Prayer, I am also developing Sati. When I sit, recognize that I am lost in thought, and then use my prayer word/mantra to release the thought to return to an “openness to God” – it seems that I am, as a byproduct, developing Sati. I am recognizing thoughts as thoughts. I am recognizing thought patterns and emotions as thought patterns and emotions. The difference between Centering Prayer and Mindfulness Meditation is that, during Centering Prayer, my primary aim is not to develop Sati. But I believe it “just happens,” as a byproduct.