Device drivers are kernel-mode tools that are created to interact with hardware. Each hardware manufacturer creates a device driver to communicate with their own hardware and translate the IRPs into requests that the hardware device understands.
One of the main purposes of any OS is to standardize the channel of communication with any type of device, regardless of the vendor. For example, if you have replaced your wired mouse with a wireless one from a different vendor, it should not affect the applications that interact with the mouse in general. Additionally, if you are a developer, you should not worry about what type of keyboard or printer the user has.
Device drivers make it possible to understand the I/O request and return the output in a standardized format, regardless of how the device works.
There are other device drivers as well that are not related to actual devices, such as antivirus modules or, in our case, rootkits. Kernel-mode rootkits are device...