Noise Cancelling or Noise Reduction when it comes to headphones

Noise-cancelling headphones use tiny microphones that identify the noise or sounds outside the headphones and then work to cancel out the sounds. Noise-reduction headphones (also known as noise-isolation headphones) reduce sound by being a barrier through which sounds cannot pass. What does all this mean? And how do these two differ? Read on over here at Bonafidereviews.