For a complete history and explanation of USB standard (1.0, 2.0, 3.0, 3.1) and port types (A, B, C, micro, etc), refer to Wikipedia USB article.

NuPrime communicates and decode digital music from the computer through USB Audio (this is a software standard, not physical USB standard). USB Audio is a software standard that defines how audio devices can communicate with the computer to play music. The USB standard and port type set the physical properties of how devices are to be connected to the computer and the speed limit.

The USB communication is always between a host and a client devices. Some devices such as smartphone or tablet can act as USB host or client device. When a smartphone is connected to the computer, it functions as a client device to the computer. Printer and USB hard drive are USB client devices. Client devices can not work with each other, unless one of the device has the capability to become a host. NuPrime's DACs (including Digital Integrated Amp) are all USB client devices and they are designed to play music from computer, smartphone or tablet. 

Some of the NuPrime models come with two Type-A ports. One of the ports is a standard USB 2.0 port (for audio, USB 2.0 is the standard and USB 3.0 is backward compatible with USB 2.0) for USB audio use. The other port is a proprietary NuPrime digital port that uses the same USB Type-A connector. It is not a USB standard! NuPrime wireless devices (Bluetooth dongle, WiFi audio receiver) use this custom digital port for 5V power as well as digital music signals (in S/PDIF format). For example, if NuPrime WR-100 is to be connected with a non NuPrime DAC, it would have to be powered by a 5V power adapter and connect its optical S/PDIF output to the DAC. But if WR-100 is connected to NuPrime IDA-8 or DAC-9, a single cable is all that is needed.

USB 3.0/3.1 is also compatible with USB Type-C, the latest plug design that’s just starting to gain adoption. This reversible plug is distinct from USB 3.1, though manufacturers may choose to support both at once. For example, the 2015 MacBook and the second-gen Chromebook support the USB 3.1 standard on their Type-C ports, while the OnePlus 2 uses the USB 2.0 standard despite a Type-C port. Don't confuse the USB standard with the port type.