SPARQL is the standard query language the most commonly used to provide interactive access to semantic knowledge bases.
A SPARQL endpoint is a standardized HTTP access to perform SPARQL queries. Developers of REST clients will find all the necessary documentation in the official W3C page for the RDF SPARQL protocol.
The Stanbol enhancer SPARQL endpoint gives access to all graphs registered to OSGi environment. For details please see Javadocs of SparqlEndpointResource.