We normally identify with the conceptual aspect of life. This conventional reality (pannatti) of names and forms: "I am a student", "my knee hurts", "I am angry" etc… is useful for functioning in the world. In mindfulness/vipassna practice, however, one is to pay attention to the true nature or ultimate reality (paramattha) of all phenomena: Instead of noticing “the pebbles under my feet” one feels the roughness (first foundation of mindfulness)  or simply “touching” (fourth foundation). Instead of the form and shape of the body, or "my knee hurts" one feels the pressure, tension or heat at the knee (first foundation)  or physical unpleasantness (second foundation) or aversion to it (third/fourth foundation). Instead of "I am angry", one experiences this emotion or mental state simply as anger (third/fourth foundation), or mental unpleasantness  (second foundation). One does not identify with these experiences as being me or mine but objectively observe them in order to understand their true nature.