oise Reduction technologies basically work by sensing the volume of incoming signals directly related to background noise and then amplifying that these signals so that they drown out or completely eliminate any other noise. They are therefore good for eliminating some types of external noises, but not useful at all against people talking nearby, amplified music etc. because those sound sources aren't what you're using the headphones for directly.
Noise-Cancelling technologies work on a different principle - essentially by sampling ambient sounds. The device will "listen" to the ambient sound waves first before generating its own opposite frequency waves which interfere with them thus producing so-called "cancellation." Again this is more effective for certain types of sounds