A Perfectly Balanced Flag 

The South Koreans may well have the most philosophical flag in the world. The white background represents Confucian 'purity' or the Buddhist concept of 'emptiness'. In the centre lies a T'aeguk, the Taoist symbol of the balance of, or harmony between opposites. It was adapted from the Chinese who usually depicted it in black and white and divided it vertically. The Korean version is more colourful and divided horizontally, with the red top half representing Yang (Heaven, daytime, masculinity, fire, activity, construction, etc). The blue lower half represents Um, or the Chinese 'Yin' (Earth, night, femininity, ice, passivity, destruction, etc).
These twin cosmic forces revolve together in perfectly balanced harmony. Although it may look like it, Oriental wisdom don't see these forces as fighting each other, but as two sides of the same coin.

The three lines at each corner are known as trigrams. These were borrowed from possibly the most important book of Chinese thinking known as the I-Ching, known in Korean as the Chu Youk.

The three unbroken lines in the top left corner symbolise Heaven
The three broken lines in the bottom right corner opposite symbolise Earth
The three lines in the top right symbolise Water
The three lines in the bottom left symbolise Fire