USB 3.0 is the widely used “Super-Speed” USB that is common. USB 3.1 was an update to that which increased the maximum power that could be used, and doubled the speed of USB 3.0. Although the technology was released in 2013, there aren’t really many devices out there yet who use it.
USB 3.1 doubles the transfer speed of 3.0 to a whopping 10 Gbps. USB Power Delivery 2.0 makes a big step forward as well with up to 100W of power. And like previous versions of USB, it is fully backwards compatible with its predecessors.
Pay attention now! USB 3.1 refers to the specification that describes the power profiles and protocols for serial communication up to 10Gbps. It also describes variety of USB connectors (Type-A, Standard-B, Mini-B, Micro-B, Standard-B 3.0, and Micro-B 3.0).
Now, USB-C, you can also say USB Type-C extends USB 3.1 by introducing a single new reversible connector (about the size of a USB Micro-B connector), power profiles that allow up to 100W, and bi-directional power flow (it can be used both to connect a charger, and to power devices).
Apple’s latest MacBook uses a single USB-C port as the place to connect the charger and USB peripheral devices.
When used with the Type-C connection, things get really interesting for 3.1. The 100W of PD v2.0 is enough to power and charge full sized notebooks, which means the proprietary AC port may soon be replaced by this universal alternative. With 4 data lanes, USB 3.1 Type-C can even carry DisplayPort and HDMI video signals, further adding to its ubiquity. Again, one port to rule them all.
So again, the USB Type-C cable and connector specification is a supplement to the USB 3.1 specification, however USB Type-C is not USB 3.1. These terms are not the same thing.
Also note, device manufacturers can choose to support USB Power Delivery and/or USB 3.1 performance but it is not required for USB Type-CTM products.
So you have to be careful. Because Type-C connections have been announced hand in hand with USB 3.1, many people assume they’re the same, or at the very least that all Type-C runs on the 3.1 spec.
This is not the case!
Remember, Type-C is just the connection type and may actually run way slower, on the speed of USB 2.0 even, so don’t assume you’ll be getting all that 3.1 goodness just because you see that tiny reversible port.