Resource Description Format
The Resource Description Format (RDF) is the W3C standard for web data. It allows for data the be linked, anywhere, and to be "grounded" in semantic descriptions of the data. The core RDF data model is very simple: It is a set of triples orgainzed into a RDF Graph. See RDF Concepts.
RDF is one of the Semanitc Web standards and the basis for Linked Open Data.