So according to some scientist from another time. Each of an atom's electrons inhabits some energy level in the atom's orbit. To ascend to or descend from one of these, that electron must emit a photon of a specific frequency as a form of energy. One could think of this like an electron living on a floor of a building of many stories. To move up or down, signifying a change in energy, an electron must receive or emit a photon of an energy corresponding with the floor or energy state that its in. This minimum energy to move the electron is a quanta of electromagnetic energy. I believe we will be exploring this further in chemistry and id be happy to report back!