in the context of atomic physics an electron will emit a discrete unit of energy (photon) when it changes to a lower energy orbit around the nucleus
this is a fundamental aspect of a laser and why its frequency band (or colour) is so narrow
when orbiting the earth, we don't expect a space ship to come back to the ground in discrete jumps. but that may well be what it is doing, but we cant observe it because the jumps are too small to be measured because the orbiting object is so large
