Electromagnetic mass

An electromagnetic mass is an object that has a lot of energy inside it, and because of this energy, the object has a lot of mass. This energy is a type of energy called electromagnetism and it is made up of tiny electric particles that move around very quickly. Usually, the objects we see around us don't have very much of this energetic mass inside them, but in certain objects like stars, the energy inside them can be so strong that it creates a huge amount of mass.