The DRV file extension is associated with driver files.
A driver is a program that interacts with a particular device or special kind of software. The driver file contains knowledge about the device or the software interface that programs using the driver don't have. A driver is often packaged as a dynamic link library (DLL) file.
Drivers for hardware are sometimes known as device drivers.
Learn more about DRV files:
See questions and answers about drivers on IT Knowledge Exchange.
Brien M. Posey explains the art of locating device drivers for Windows computers.
Serdar Yegulalp shows you how to install device drivers on Windows 7.
DriverGuide.com provides many printer and other device drivers for downloading.