THUNDERBOLT EXTERNAL DRIVES
Thunderbolt 3 USB Type-C plug
Thunderbolt 3 was developed by Intel and uses USB Type-C connectors. Compared to Thunderbolt 2, Intel's Thunderbolt 3 controller (codenamed Alpine Ridge) doubles the bandwidth to 40 Gbit/s (5 GB/s), halves power consumption, and simultaneously drives two external 4K displays at 60 Hz (or a single external 4K display at 120 Hz) instead of just the single display previous controllers can drive.
THUNDERBOLT DRIVES
Thunderbolt 1 and 2
At the physical level, the bandwidth of Thunderbolt 1 and Thunderbolt 2 are identical, and Thunderbolt 1 cabling is thus compatible with Thunderbolt 2 interfaces. At the logical level, Thunderbolt 2 enables channel aggregation, whereby the two previously separate 10 Gbit/s channels can be combined into a single logical 20 Gbit/s channel.