What's inside a DICOM file
A DICOM file has two parts: a header and a pixel buffer. The header is a list of tagged fields — patient demographics, study description, modality, image dimensions, slice thickness, voxel spacing, hundreds of others. The pixel buffer is the raw image, often in 16-bit signed integers for CT/CBCT.
A 3D study like a CBCT scan is usually one DICOM file per slice (200–600 files), or one multiframe file containing the whole volume. Both forms are valid and any standards-compliant viewer reads either.
Why DICOM matters for sharing
Sending a DICOM means the receiver gets the exact same data the scanner produced. No re-encoding, no compression artifacts (unless explicitly chosen), no loss of measurement accuracy. Window/level can be adjusted on the receiver side because the raw Hounsfield-like values are preserved.
JPEG, PNG and PDF screenshots discard the raw values. Once converted, the recipient can't adjust contrast, measure in mm, or reconstruct in another plane. That's why specialists insist on DICOM, not screenshots.