There are lots of different types of scanners from the basic ccd plugged into your computer to the very rugged, ‘drop me off a 4 storey car park and I will still work’ barcode scanning computer.
Mostly it depends on your price and what you want to use the scanner for.
If, for example, you are a library with limited budget and you only need to scan a library card and book when they are presented at your main then a CCD scanner might be just what you are looking for. They connect to your computer via a usb cable and you can mount them on a stand or hold them in your hand to scan when required. As a basic scanner they do the job, don’t cost much and when they break (as occasionally happens) they are easy to repair or replace.