It doubles the bandwidth of USB 3.0 to a stunning 10Gbps. It comes with a USB-A and a new generation USB-C connector. USB-C is reversible and so no need to worry which direction to plug in. USB-C is also better than USB-A that it increases the current from 900mA to 3A.
More devices will be supported in bus-powered mode and charging will be much faster. For new MacBook and the new Chromebook Pixel user, your USB-C accessories will also work in your PC.