Binary entropy ($h_2(p)$)

The binary entropy function is the information entropy of a Bernoulli random variable:with endpoint values zero. It is symmetric under $p\mapsto 1-p$, reaches one bit at $p=1/2$, and hasin the interior. Its strict concavity expresses why an even mixture of two outcomes has more uncertainty than a strong bias toward either one. The curve in mutual information also shows how this same uncertainty becomes the loss term in binary symmetric channel capacity.