Know about conductors and insulators. Know which materials are magnetic. This is because it is much easier to produce AC voltage using electromagnetic means. AC voltage moves positive and negative. We use devices to change voltage from AC to DC when we need it.
Magnetic fields originate from moving charges.
Only moving charges feel a force in a magnetic field, not stationary charges. There is no force if the velocity is along the same direction as the magnetic field. These equations also prove that light basically consists of electric and magnetic field. Light is part of electromagnetism. Average speed describes the speed over some time period.