The iPad can scan documents that you need to share with someone. It's a super convenient way to scan and email a document you got in the mail or even that you need to sign.
You can use the built-in Notes app to scan or if you do a lot of scanning an app like Scanner Pro.
This is better than taking a picture of the document, and it delivers a photo or PDF that looks like you scanned it with a printer or an office scanner.
With Scanner Pro, you can more easily capture multiple pages and save to different locations, but for the average user, this is a quick and free option. You can also use the Continuity camera feature in macOS to use your iPad to scan straight into a document on your Mac.