Given an elliptic surface, the set of sections of its fibration forms a group called the Mordell-Weil group. After recalling the main concepts from part I, I will expose the main properties of this group, with a special focus on torsion sections. I will give two constructions on quartic surfaces which appear naturally in the study of the enumerative geometry of lines, where torsion sections play a prominent role. The talk will be aimed at students who took a first course in algebraic geometry.