About the Thunderbolt ports on Mac
You can use the Thunderbolt port on your Mac to connect a display, a TV or a device, such as an external storage device. And with the appropriate adapter, you can connect your Mac to a display that uses DisplayPort, Mini DisplayPort, DVI, HDMI or VGA.
About Thunderbolt 3 (USB-C)
The Thunderbolt 3 (USB-C) port is available on some newer MacBook and iMac computers. The port allows data transfer, video output and charging through the same cable. For information about which adapters work with the Thunderbolt 3 (USB-C) port , see About USB-C on Mac.
Use only Thunderbolt cables with Thunderbolt devices, and only Mini DisplayPort extension cables with Mini DisplayPort devices. If you use the wrong cable, the device won’t work even though the cable’s connectors fit your device and your Mac.
About power cables
The Thunderbolt port on a Mac can provide power to multiple connected Thunderbolt devices, so separate power leads from each device are usually not required. Check the documentation that came with your device to see if the device needs more power than the Thunderbolt port provides.
If you have a portable Mac
Using a Thunderbolt device without its own power cable can cause the battery on your portable Mac to become depleted faster. If you plan to use such a device for an extended period, it’s a good idea to connect your portable Mac or your Thunderbolt device to a power source. When connecting a Thunderbolt device to a power source, be sure to disconnect the device from your Mac first, connect the device to a power source, then reconnect the device to your Mac. Otherwise, the device continues to draw power from your Mac.
About connecting multiple Thunderbolt devices
You can connect multiple Thunderbolt devices to each other, then connect the chain of devices to the Thunderbolt port on your Mac.
Only the device directly connected to your Mac receives power from the computer’s Thunderbolt port. The other devices in the chain must be powered by separate power adapters.
A DisplayPort device must be the last device in a chain of connected Thunderbolt devices. For example, if you want to connect both a Thunderbolt hard disk and a DisplayPort display to your Mac, connect the display to the hard disk and then connect the hard disk to your Mac.
If you use Boot Camp
If you use Boot Camp to run Windows on your Mac, see the Apple Support article Adapters for the Thunderbolt 3 (USB-C) or USB-C port on your Mac.