This is a slider crank mechanism except that there are different ways to describe it. It can either be represented by two bodies, two revolute joints and one special combination joint which allows one rotation and one translation, ( not necessarily about the same axis, as in case of a cylindrical joint); which makes it a one degree of freedom mechanism; or as a three body linkage with 3 reolute joints and one translational joint, which also makes it a one degree of freedom mechanism.