Three ways natural selection picks a phenotype?

stabilizing selection: when individuals near the center of the curve have a higher fitness than individuals at either end of the cure, keeping the center at its current location but narrows the overall graph

directional selection: when individuals at one end of the curve have a higher fitness

than individuals at the other end, or middle, causing the entire curve to move as the character trait changes

disruptive selection: when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle, causing the single curve to be cut into two

These three types of selection are brought about by natural selection, so whichever one is favored, then the genes evolve in that specific direction. natural selection acts on the genotype, but the results are seen in the phenotype