It is basically creating or representing physical things such as paper documents (health records, identity cards, location data, and legal documents), microfilm images, photographs and more into a digital format which then can be used by a computing system for numerous reasons.
Digitizing doesn’t mean replacing the original document or image, etc. However, these original documents sometimes ages and the writings do fade away or gets destroyed by unforeseen circumstances. But after having digitized a paper document you can destroy it or keep it, depending on, for instance, legal requirements.
We mainly digitize by using document scanners, you can also for instance, scan or simply take a picture with your smart handset (mobile phone). These document scanners create a digital representation of a scanned document, or a photograph but it doesn’t stop there, it goes through processes, after all why scan a document if you don’t use the data it contains.