What is fudgy vs cakey brownies?

The two ends of the brownie texture spectrum. Fudge brownies have a dense, glossy, barely-set interior — high fat, low flour, minimal leavening. Cakey brownies have an open, springy, crumbly interior — more flour, more eggs, more baking powder. Which one you get is mostly controlled by three knobs: butter ratio (higher = fudgier), egg ratio (more = cakier), and baking powder amount (less = fudgier). The library default is firmly fudge-brownie territory; dial baking powder up to 3-4% of flour and eggs up to 130-150% of flour for a cakier result without changing the rest of the recipe.