Essence, Qi, and Spirit are the three treasures of the human body. All cultivators' cultivations are based on these three elements. Regardless of which aspect their cultivation focuses on, they will balance it by cultivating the other two as well. Generally speaking, except for those who genuinely struggle to cultivate all three due to certain reasons, most cultivators would choose to practice them simultaneously.
After explaining the way of Body Refining, Pei Xuanjing shared his understanding of Refining Qi and Refining Spirit.
However, these two aspects are currently the most common practices among the cultivators of Heaven and Earth. Whether it's the Xiantian Nature of the Xuantian Sect, the Talisman of Dragon Tiger Mountain, or the Sword Qi of the Sword Sect, they can all broadly fall under this category.