Thunderbolt 3 combines ultra-high bandwidth with the ultra-versatility of the USB-C industry standard to create one revved-up universal port — and MacBook Air has two of them. Thunderbolt 3 integrates data transfer, charging and video output in a single connector, delivering up to 40 Gbps of throughput for twice the bandwidth of Thunderbolt 2. Existing devices are easily connected with a cable or adapter. And Thunderbolt 3 is reversible, so no matter how you plug it in, it’s always right side up.
SOURCE: APPLE