The bagua are eight diagrams used in Taoist cosmology

Cosmology

Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 to represent the fundamental principles of reality, seen as a range of eight interrelated concepts. Each consists of three lines, each line either "broken" or "unbroken," representing yin

Yin and yang

In Asian philosophy, the concept of yin yang , which is often referred to in the West as "yin and yang", is used to describe how polar opposites or seemingly contrary forces are interconnected and interdependent in the natural world, and how they give rise to each other in turn. Opposites thus only...

 or yang, respectively. Due to their tripartite structure, they are often referred to as "trigrams" in English.

The trigrams are related to taiji

Taiji

Taiji 太極 is a Chinese cosmological term for the "Supreme Ultimate" state of undifferentiated absolute and infinite potentiality, contrasted with the Wuji 無極 "Without Ultimate"...

 philosophy and the wu xing, or "five elements".