A driver is a special type of software. Whenever your PC needs to connect to
and control a peripheral device like a printer or scanner the driver written to
work with it is required.
The level of the driver needs to be matched to the level of the device it is controlling. Some drivers are backward compatible. HP has done a good job with its PCL (printer control language) by making each successive PCL version backward compatible with earlier versions of printers. This can save a lot of headaches for you.
If you lose a driver or have the wrong one installed your peripheral device becomes a 10 pound paper weight.
So what do you do if you need a driver? Try going to the hardware manufactures website and looking for a link to drivers. You may have to click around a lot to get to the right spot depending on teh organization of the web pages. Once you do you'll need to enter the model of the hardware you seeking the driver for. Then you can download and install it following the instructionm that come with it.