Qi is the flow of your body’s energies. Qi is divided into Yin and Yang, sort of positive and negative, female and male energies that combine to form the whole Qi. Qi can’t be seen, because it is energy. But Qi can be tracked.
Chinese herbs help unblock channels or clear away excessive stagnation. In depression its thought that the person’s Qi becomes slow, so Chinese herbs help get the qi moving.