Yes, USB 3.0 is backward compatible to USB 2.0 for the connectors and protocols. This is achieved by including an additional 5 pins stacked on top of the existing USB 2.0 connections.
For more details on USB, we’ll refer you to the WikiPedia page – USB – Wikipedia
Of course, a USB 2.0 device will still only operate at USB 2.0 transfer rates whether it is plugged into a USB 3.0 port or a USB 2.0 port. Similarly, the only way to achieve USB 3.0 speeds is to use a USB 3.0 device in a USB 3.0 compliant port. Generally, you expect at least a 12x increase in your transfers using compliant USB 3.0 devices compared with USB 2.0.