What is the role of each type of potting medium? A detailed explanation

　　1.OrchidsMud: soil formed from decayed leaves that accumulate in the hollows of mountain rocks; it is soft, free-draining and fertile, with a pH of 5.5-6.5. 2. Fire-baked soil: granular soil left after the surface soil of raw weeds is baked over fire. 3. Xiantu (immortal soil): granular soil mined and processed in Mount Emei, Sichuan; available in large, medium and small grades. 4. Pine and cypress orchid stone (volcanic stone): produced in Taiwan, China; available in large, medium and small grades. 5. Kongji stone: produced in Taiwan, China; a continuous bubble body made from high-mountain mineral soil as raw material through technical processing. Available in large, medium and small grades. 6. Zhijinshi (plant gold stone): produced in Japan; available in large, medium and small grades. 7. Emperor stone: produced in Japan; a natural breathable porous stone. 8. Perlite: strong drainage, moisture-retaining, with fairly good air permeability.