There is a huge list of generic identifications that it can use, or it can say other, and transmit an additional code. It will send a response with an identifaction code. The other end of the USB cable, the device, will have a controller chip that handles the communication of the port. When you connect a USB device to your computer, the computer will first supply 5v over the port and data to request an init. VCC, Data+, Data- and Ground, where newer specifications will have more bandwidth and power transmission. USB, aka Universal Serial Bus is a connection of 4 ports.
