What is a driver?
Drivers are the programs that allow your operating system to communicate with hardware devices. They tell the operating system what device has been installed as well as their function.

Windows has already installed a driver for a device, should I update it?
Drivers provided by Windows can only offer basic device performance. For optimal performance, you must install the latest drivers provided by the manufacturer. The most important thing to note is that the drivers provided by Windows do not contain a control panel for hardware configuration. For example, if you don't install the latest drivers provided by the manufacturer for video cards, you cannot configure the OpenGL and Direct3D options for the video card. This can noticeably lower the quality and FPS of 3D images in games. Similarly with the sound card, Windows drivers cannot offer EAX sound effects, 3D sound effects, or Dolby multi-channel surround stereo. So installing a suitable driver will enhance the full performance of device.