Three placeholder roles say where a URI comes from and what it stands for. nt:LocalResource marks a resource minted under the new nanopublication's own URI, so the user only types a short name for it.

nt:IntroducedResource additionally records the resource in the publication info with npx:introduces: this nanopublication brings the thing into existence, and the thing has an identity of its own that others can refer to. nt:EmbeddedResource records it with npx:embeds instead: the resource is content that belongs to this particular nanopublication.

The difference shows when a nanopublication is superseded. An introduced resource keeps the same URI in every later version, so a new version must refer to the original URI rather than mint another; an embedded resource is expected to get a new URI with each version.