Glossary
Invisible Watermark
Short answer
An embedded, invisible marker identifying an image as AI-generated.
Many tools embed an invisible marker in the images they produce. Google's SynthID and Content Credentials under the C2PA standard are the most common examples.
The purpose is not to restrict use but to make provenance detectable. You can use the image normally; the marker is only readable with the right tools.
Some platforms read these markers and label content as AI-generated. For news and anything making a factual claim, that transparency is useful.