Most headphones are Closed-back. The headphone's unit is structured in such a way that the speaker is mounted against a solid cup. The speaker drivers in headphones usually emit sounds in two directions: towards your ears, and towards your surroundings. In the case of Closed-back headphones, the noise is largely blocked out and the sound is directed just towards your ears. These aspects enable the headphones to produce a heavier bass sound.
Thus the Closed back headphones are specifically designed to completely isolate outside noise, making them a perfect choice for commuters. These don't actively cancel out noise, but definitely do so passively. Because of the fact that most closed back headphones are over-ears and are generously padded, these provide noise isolation of around 10dB. This level of isolation helps DJs, music producers and those who probably just want to zone out
So with all the sound directed towards you and ambient noise isolation these headphones offer, your music just sounds way better without any noisy interruptions. And the best part, this wont let any beat escape and disturb anyone around you. This helps especially in the case of gaming headphones: No sound escapes, hampering the speech clarity of the Mic, which might pick up the sounds that escape in case of open back headphones.