  We give a structure theorem for the $m$-torsion of the Jacobian of a general
superelliptic curve $y^m=F(x)$. We study existence of torsion on curves of the
form $y^q=x^p-x+a$ over finite fields of characteristic $p$. We apply those
results to bound from below the Mordell-Weil ranks of Jacobians of certain
superelliptic curves over $\mathbb Q$.
