USB3.1 (also called Gen.2) brings many improvements to the previous standard USB3.0 (Gen.1). The most noticeable is the new Type-C connector which is much smaller than the previous standard connectors, it is also reversible.
The new Type-C Alternative Mode allows the USB cable to carry different types of signal, including native DisplayPort capable of 4k resolution video.
USB Power Delivery v2.0
The USB3C-901 supports up to 20V / 3A (60W) of power. The new improved power delivery allows you to charge not only small mobiles devices such as mobile phones and tablets, but also laptops.
The new USB Type-C connector is smaller than most of the previous USB connectors. (Micro B is the exception.) It is also symmetrical; this allows you to plug the connector in either way up.