Both 'noise-isolating' and 'noise-cancelling' headphones aim to reduce how much sound from the outside world gets into your ear and subtracts from your listening pleasure. The reason these technologies have different names is because they attack the problem of ambient noise in very different ways.

Noise-isolating headphones use a piece of thick foam around the earpiece to block out ambient noise before it enters the ear canal. The seal between your ear and the earpiece needs to be tight, so most companies ship earpieces of varying sizes for you to select the most comfortable one. These kinds of headphones can significantly improve your listening experience, require no batteries to function and usually cost less than noise-cancelling models.  

Noise-cancelling headphones use electronics to filter out the surrounding noise. They have tiny microphones built inside them that sample the ambient noise, invert the sound waves and play them back alongside the music you're listening to. The natural ambient sound and the inverted ambient sound produced by the headphones cancel each other out, hence the name 'noise-cancelling'. They need to be powered by batteries.

We recommend you always test out the effectiveness of any possible purchase before you buy, and consult our reviews for the best advice on individual products -- our high-tech headphones round-up would be a good place to start.