Perceptual fingerprints, in plain language
A perceptual fingerprint describes what an image looks like, rather than its exact bytes.
How it differs from a hash
A cryptographic hash changes if a single pixel changes. A perceptual fingerprint is built to stay similar across resizing, compression, and mild cropping — so it can help recognize visually related versions even when the exact file has changed.
What it doesn’t prove
Two images with similar fingerprints are visually related — not necessarily copies, and not necessarily infringing. Visual similarity is a research lead, never proof of copying.