Headphones allow a single user to listen to an audio source privately. They generally come in 2 forms, circumaural and supra-aural. Circumaural headphones completely encumber the ear and black out background noise. Supra-aural headphones sheath the surface of the outer ear but don’t completely seal them in so are more prone to background noise leakage.
Headphones can be further differentiated by their type of ear cups - Closed back headphones mean the outer part of the cups have a hard enclosure which reduces the amount of sound leakage. Open back headphones allow your ears to breath as the outer part of the cups are left open giving you a more natural sound. Semi-open headphones are considered a compromise between open-back and closed-back.
Closed back headphones are more coloured than open back designs, but also isolate the listener and restrict sound leakage. This makes them ideal for tracking, recording or even just for listening whilst outside of the studio.
Headsets usually comprise of lightweight headphones and a microphone.