The graph uses a logarithmic frequency scale, so the octaves where human hearing is most sensitive get useful room instead of being squeezed against the left edge. Adjust the FFT size for the tradeoff you need: larger transforms separate nearby frequencies more clearly, while smaller transforms respond faster to short changes.
The seven-band table turns the moving graph into a readable snapshot. Sub bass covers 20 to 60 Hz, bass reaches 250 Hz, and the midrange is divided around common vocal and instrument regions. These are practical production labels, not hard acoustic boundaries.