Drivers allow communication between your hardware and operating system.
A driver is a type of software that allows the computer to interact with the hardware which comprises your system. Having the correct driver is crucial for both your internal and external hardware devices. Updated drivers allow these devices to communicate with the software that makes up your Operating System. Most devices will have the necessary drivers correctly installed with purchase of a computer; however, new hardware and upgrades to the operating system may require that you update the drivers. Having the newest drivers for your devices will typically enhance the performance and stability of your computer.
Some drivers do not need to be updated unless you are encountering a specific problem with that devices. For example, motherboard drivers or internet adapters rarely need to be updated unless you are having an error directly caused by that driver.