What does this equation mean?

Shortening the electrical path this way has a direct, quantifiable effect on how much bandwidth a given joint area can carry. Treating the joint as a grid of independent connections at pitch p , each connection occupying roughly $p^2$ of area, gives a first-order areal bandwidth density $B_A \;\approx\; \frac{f_b}{p^{2}}$. where $f_b$ is the data rate carried by a single connection. The relationship is quadratic in pitch, not linear: halving the pitch alone — with no change to the per-connection data rate — quadruples the number of connections available in the same area, and therefore roughly quadruples aggregate bandwidth density. That is why the packaging industry has spent so much engineering effort on pitch specifically, rather than on pushing more current or a faster signal through the connections that already exist: geometry, not signalling rate, is the cheapest source of additional bandwidth once a joint is already short and direct.