What is a driver? – Windows drivers | Microsoft Learn

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.

https://learn.microsoft.com/en-us/windows-hardware/drivers/gettingstarted/what-is-a-driver-