Before earbuds like the AirPods came along, wireless earbuds had a cord between the buds. They were wireless because they offered wireless Bluetooth streaming and didn't have a headphone cable that plugged into your device. Some companies still make those types of wireless earbuds -- the Beats Flex is one example -- and some people like having a cord that allows the buds to dangle from your neck when not in use. True wireless earbuds have no cord between them. They are entirely cord-free and link wirelessly to create a stereo pair. They are sometimes referred to by the acronym TWS, which stands for true-wireless stereo.