From Latin redigere (originally "to compile or draft"), redaction now means obscuring specific elements — SSNs, faces, license plates, privileged text — so recipients cannot recover them. It differs from deletion (data gone entirely) and from anonymization (the legal outcome where a person can no longer be identified by any means). AI tools accelerate visual redaction via detection and motion tracking, but weak blur can be reversed by de-pixelation models — proper redaction flattens the file so nothing recoverable remains.