Maxwell's equations, written in 1873, summarize what we know about electricity and magnetism. They relate the electric and magnetic fields to electrical charges and currents and to each other. These fields produce forces on charged particles. Maxwell's equations played an important role in the development of special relativity. These equations imply the existence of wave solutions when you are far away from charges and currents. These waves can be interpreted as light waves. They propagate at a constant speed which is the same in any (inertial) frame. Remarkably, one can determine the speed of light by measuring the force between two charges and the forces between two currents. If you want to learn more about this than what we showed in class, you may browse through the second volume of Feynman's Lectures.