The Setting For the purposes of this discussion, let's assume that the He3 fusion plants have been proved out, and folks are frantically building them, just waiting for us to show up with with tanks full of helium-3. We'll assume you understand that atoms are made up of protons, neutrons, and electrons.
Electrons are the very lightweight, negatively charged bits that buzz around the edges of an atom.
Regular chemical reactions work by trading and sharing electons among atoms. For instance, when you burn a piece of paper in air, the chemical reaction involves some carbon atoms in the paper sharing electrons with some oxygen atoms from the air. The reaction forms carbon dioxide gas while the electons give off energy, as heat and light, when they change their orbits. Protons and neutrons make up an atom's nucleus. Generally, the neutrally charged neutrons keep the positively charged protons from fighting each other.