The terms scan, scans, scanner, and scanning are used in many places in multiple ways at DP.
"Scan" and "scans" (n.) usually refer to the image files created by Content Providers (occasionally referred to as "scanners" [n.], in the sense of people who scan [v.]), who use hardware known as "scanners" (n.) to "scan" (v.) the individual pages of a book or other textual material. This process is referred to as "scanning" (v. or gerund). In other words, "scans" are the results of running a "scanner" or "scanning." (Sometimes Content Providers harvest scans from other online sources instead of scanning them themselves.)
OCR software is used to create an OCR text from the scanned images (scans). As a project begins its journey through DP's rounds, the proofers working in P1 compare each page's OCR text to its original scan. Thus, "the scans" are the foundation of the e-texts produced by DP.
The DP workflow is focused, at its core, on individual scanned images of the pages of books (and other published works). Associated with every page of a DP project is a page scan for each page in the original work. If the original work is illustrated, higher resolution illustration scans will also be part of the project.