Binaural, stereo, or both?

Binaural headsets have two "speakers." When on a phone call, you hear the other person through both of your ears and the sound seems to be centered in your head. The two speakers are wired together, and they reproduce the same sounds.
Binaural headsets are important for noisy environments, or situations where you want to concentrate on a phone call without being distracted or annoyed by people near you.
Stereo headsets (or headphones) also have two speakers, but they are wired separately, so they can reproduce different sounds.
Although you'll hear voices through both ears with a binaural headset, you do not get true stereo sound (different sounds through each ear), which is preferable for music, games, and sometimes for teleconferencing.
Pay attention to product descriptions so you get the right thing.