In the most fundamental sense, a driver is a software component that lets the operating system and a device communicate with each other. For example, suppose an application needs to read some data from a device. The application calls a function implemented by the operating system, and the operating system calls a function implemented by the driver. The driver, which is usually written by the same company that made the device, knows how to communicate with the device to get the data. After the driver gets the data from the device, it returns the data to the operating system, which returns it to the application.