The Google USB Driver is required for Windows only in order to perform adb debugging with any of the Google Nexus devices. The one exception is the Galaxy Nexus: the driver for Galaxy Nexus is distributed by Samsung (listed as model SCH-I515).
Windows drivers for all other devices are provided by the respective hardware manufacturer, as listed in the OEM USB Drivers document.
Note: If you're developing on Mac OS X or Linux, then you do not need to install a USB driver. To start developing with your device, read Using Hardware Devices.
