The vital life force or energy that flows through the body along pathways called meridians. When Qi is balanced and flows freely, the body is healthy; when it is blocked or unbalanced, illness can occur.

The concept of duality and balance, representing opposite forces that are interconnected and interdependent. Yin is associated with qualities like cold, dark, and passive, while Yang represents heat, light, and activity. Health is achieved when Yin and Yang are in balance.

Wood, Fire, Earth, Metal, and Water, which are thought to correspond to different organs and systems in the body. The balance and interaction between these elements are essential for health.

TCM classifies organs into two groups: Zang (Yin organs) and Fu (Yang organs). The Zang organs (like the heart, liver, spleen) are responsible for storing vital substances, while the Fu organs (like the stomach, intestines) are involved in transformation and transportation.

The body is crisscrossed by meridians, channels through which Qi flows. Acupuncture points (acupoints) are specific locations on the body where needles can be inserted to influence the flow of Qi.