The ‘triples’ of RDF data can be stored in a specialised database, called a triple store, against which queries can be made in the query language SPARQL.

Source: ODH

A triplestore is a purpose-built database for the storage and retrieval of triples through semantic queries. A triple is a data entity composed of subject–predicate–object, like ‘Bob is 35’ or ‘Bob knows Fred’. Much like a relational database, information is stored in a triplestore and retrieved via a query language. Unlike a relational database, a triplestore is optimised for the storage and retrieval of triples. In addition to queries, triples can usually be imported/exported using RDF and other formats.

Source: http://en.wikipedia.org/wiki/Triplestore