BaZi basics
Every BaZi chart has one character at its center: the day master (日主) — the heavenly stem of the day you were born. Ten are possible: the five elements (wood, fire, earth, metal, water), each in a yang and a yin form. Jia and Yi are wood; Bing and Ding are fire; and so on.
The day master is the "I" the chart is arranged around. Every other stem and branch is read by its relationship to this one: what feeds it, what it controls, what pressures it. Two people born in the same month can read entirely differently because their day masters differ.
It helps to hold the day master as a temperament in the oldest sense — a weather of the self. Yang wood reaches; yin wood adapts. Yang fire shines publicly; yin fire glows privately. None of the ten is better: each is a different way of standing in the world, with its own graceful expression and its own signature blind spot.
A fair reading never stops at the day master. Its strength (whether it is "in season", rooted, supported) and the balance of elements around it modulate everything. The day master is the instrument; the chart is the acoustics of the room it plays in.