rdf:resource is a Production syntaxTerm (not a concept), that is an RDF/XML attribute the value of which is interpreted as a RDF
URI reference object node.
<rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar" dc:title="RDF/XML Syntax Specification (Revised)">
<rdf:Description ex:fullName="Dave Beckett">
rdf:resource attribute indicates that the property element's
value is another resource, identified by its URIref. Because the URIref is being
used as an attribute value, RDF/XML requires the URIref to be written
out (as an absolute or relative URIref), rather than abbreviating it as a QName.