View full size image. Measured by surface area, the Caspian Sea is the world's largest inland water body. The sea covers roughly 143,200 square miles (371,000 square kilometers) and borders five countries: Iran, Russia, Kazakhstan, Turkmenistan and Azerbaijan.
A logical device driver is a high level abstraction of how a device behaves. A physical device driver is a driver for a specific piece of hardware. The logical device driver talks to the physical device driver for you to keep you abstracted from the underlying hardware. For example, there are many different types of printers, and they typically come with their own drivers.
In a computer, a driver is a piece of software that tells hardware how to run on a certain operating system. That means your PC card, DVD drive, video card and other hardware all use drivers to make their operations work. If you're using your computer right now, you probably have a ton of drivers already installed and working.