You are not the only person confused. USB Type C (commonly USB-C) is the connector which tells you nothing about what that connector is capable of. USB-C is simply a connector, nothing more, nothing less. It is the hardware connected to that connector that defines what you can do with it. For instance, a USB-C connector can support Thunderbolt 3 and USB 3.1 but just because you have a USB-C connector doesn't mean you have Thunderbolt 3 and USB 3.1 (see the MacBook, for instance). I have seen PCs with USB-C connectors that only support the USB 2 protocol; imagine that users potential disappointment.
Intel choose the USB-C connector as the connector for Thunderbolt 3. Calling the port USB-C is accurate if only that it is describing the connector, not the capability.
Heads up, if Thunderbolt 3 IS supported in the new MBPs USB-C connectors you can't use just any USB-C cable for Thunderbolt; you guessed it, you need a proper Thunderbolt cable. Oh, and be aware you can buy USB-C cables that actually only support the USB 2 standard, so if you try to connect an actual USB 3.1 device you are in for a disappointment. In fact, there are a number of absolute crap USB-C cables and devices out there which could potentially cause damage to the host device (read: your brand new MacBook Pro). Amazon is taking a stand to ensure what they are selling meets the standards set out by the USB council.
Hope this helps.