This is an intro to UMBEL (Upper Mapping and Binding Exchange Layer), a lightweight ontology for relating Web content and data to a standard set of 20,000 subject concepts. Connecting to the UMBEL structure gives context and coherence to Web data. Via UMBEL, Web content, data and metadata can be linked, made interoperable, and more easily navigated and discovered. These subject concepts have defined relationships between them, and can act as semantic binding nodes for any Web content or data. The UMBEL subject concepts are derived from the OpenCyc version of the proven Cyc knowledge base.