Thunderbolt 3 uses the USB-C connector, but not all host connections, cables, and devices with a USB-C connector support Thunderbolt 3. This means that a USB-C device is compatible with a Thunderbolt 3 host connection, but a Thunderbolt 3 device is not compatible with a USB-C host connection. Therefore, it is important to know whether you have a USB-C or a Thunderbolt 3 host, cable, or device.
To determine if your component is a Thunderbolt 3 device, look for the Thunderbolt 3 symbol (shown below). USB-C devices do not include this symbol. For more information about USB-C, see the following FAQ: http://www.startech.com/faq/usb-c-port-capabilites.
Thunderbolt symbol: https://sgcdn.startech.com/005329/media/products/gallery_large/TBLT3MMXM.B.jpg.