Both these terms sound curiously similar, and do have to do with the transfer of electromagnetic radiation from a body, such as a star. Emission is what happens when the atoms involved within the body, such as a star, move to a lower energy state. There is a release of energy, usually in the form of a photon, which is a tiny energy packet. This energy emits from the atom in the form of radiation, generally away from the atom. Transmission is what happens when the body sends all these tiny packets of energy away from itself in the form of raidation. Think of it as "mass marketing" of photons away from the star, radiating outwards into space. So emission is what happens singularly, on a small scale, to one atom, as it moves to a lower energy state during nuclear fusion, while transmission involves collectve transportation of large numbers of the products of emission.