The t'aeguk pattern is the central component in the Korean national flag. It is also often seen on residential and temple gates, memorial red arches at royal tombs and shrines, the gates of Confucian academies and schools, and the lattice doors of Buddhist lecture halls, as well as on handicrafts.

The basic characteristics of the t'aeguk pattern are the red comma shape, the male element, and beneath it the blue comma shape, the female element, both of which interlock in a circle to express infinite movement. As mentioned above, t'aeguk is a symbol incorporating cosmic dual entities-that is, heaven and earth, the positive and the negative, and the male and the female. It is the Great Ultimate, the law of cause and effect, where things begin and end. These dual forces of the cosmos, it was believed, were the fountains of human life. As it circles endlessly, the t'aeguk was an image of immortality as well.

The scholar Zhou Dun-yi (1017-1073) of the Song Dynasty has been credited with introducing the t'aeguk (taiji in Chinese) symbol in his book Taijitushe (An Explication of the Taiji Symbol). But a Korean t'aeguk design has been found from much earlier, the seventh century. There is a stone carved with the t'aeguk in the compound of Kamunsa temple, built in the 50th year (628) of King Chinp'yong of the Shilla Kingdom.

The um and yang in t'aeguk represent the two extreme elements in harmonious relations. Their interlocking symbolizes the perfect union and interaction of the polar extremes of male and female. The red on top symbolized heaven, or male, and the blue underneath symbolized earth, or female.

T'aeguk principles were believed to govern the everyday affairs of life. The combination of altruistic communal cooperation with pursuit of self-perfection is rooted in those principles, perfection: through the harmony of extremes.