The meanings of changing yang lines
The meanings of changing yin lines
Every hexagram is built up in 6 steps, 6 lines. Every line, when changing, turns hex. 1 into another hexagram. In old texts, the place of the lines is referred to as "hexagram 1 its 44" (bottom line) "its 13" (line 2) and so on. Every line is the expression, in the time of hex. 1, of this second hexagram. This hexagram is called the ZhiGua (zhi means its, his, her, and gua means hexagram).
I have put the line text and the "ZhiGua" side by side, so it is easy to see the connection.