Device drivers
Have you ever bought a peripheral (any piece of hardware e.g. a webcam, a camera, a printer) and plugged it into your computer, only for it not to work? There could be a number of reasons, but one of the most common is that your computer doesn't have the right 'driver' for the hardware you plugged in. A driver is a piece of software that allows a particular piece of hardware to talk to the operating system and hardware already on your computer so that it can then work properly in your computer. Without the right driver installed, the hardware will probably not work.
Operating systems like Windows come with many drivers already installed. These are known as 'generic' drivers, because each one is designed to work with most pieces of equipment. For example, the generic mouse driver in Windows will allow you to plug in almost any mouse and it will just work without you having to do anything! Of course, if you have a special mouse with some extra buttons or features, it may not work at all or may only partially work. If you have bought some amazing new piece of equipment that is really new and cutting edge, it might be that there isn't a generic driver for that piece of equipment yet in your operating system. It could also be the case that you have a piece of equipment that is using an old driver and you need to update it to the latest one for your equipment to work properly.
When you plug a peripheral into your computer, your operating system will detect this. It will then check if there is a suitable driver already installed. If it can't find one, or detects that the driver is old, the OS may ask you if you have a disk with a driver that it can use or whether it should look on the Internet for one to download. Once you have the latest driver installed, you can test your hardware to see if it works in the computer. Sometimes, you have to re-boot your computer for the driver to work properly but most of the time, you can just use your plugged-in peripheral.