The SoundSport Wireless are wireless sport earbuds that are very similar to the SoundSport Free. Instead of being true wireless earbuds, however, the two SoundSport Wireless earbuds are tethered together by cable. Aside from that, the two wireless earbuds have similar audio performance and use the same Bose Connect app. The SoundSport Wireless will last longer on a single charge (as opposed to the SoundSport Free which recharge every time they go back in their case).
Earbuds have small speakers that rest on the ear canal of the wearer. These are usually much less expensive than on-ear and over-ear headphones and reproduce the sound well. However, outside sounds, such as traffic or power tools, can get past the earbuds and interfere with your enjoyment. Earbuds also don't stay in place very well if the wearer is moving much, such as exercising. These also are lower fidelity than on-ear and over-ear headphones.