So what exactly is “provenance research?” Most simply, it is research into the ownership history of a work of art (or decorative object, antiquity, book, etc.). The term “provenance” derives from the French provenire, meaning “to originate.” A provenance comprises the historical record not only of an object’s past owners, but also of 
any transactions by which the work changed hands—a dealer who handled the sale of a particular work, for instance. Ideally, a provenance goes back to the artist and continues to the present owner; such a complete, unbroken provenance is rare, however. Establishing the provenance of a work of art has bearing on that work’s monetary value and authenticity/attribution: a complete provenance back to the artist can prove authenticity and therefore enhance value. A questionable or falsified provenance can cast doubt on the authenticity of a work.
What do gaps in a provenance mean? Sometimes, nothing; not all objects have a discoverable provenance, and sometimes documentation of ownership simply does not (or never did) exist. Nonetheless, all gaps must be examined critically. In particular, because of the looting and confiscations of art perpetrated on a massive and unprecedented scale by the Nazis, gaps from the period 1933-1945 in Europe are potentially problematic and must be thoroughly investigated.
Provenance research is by nature interdisciplinary. Beyond traditional art historical and archival resources, auction and dealer records, genealogical and historical materials, and biographical resources are all often consulted when conducting provenance research. A knowledge of contemporary history, especially in the case of World War II-era provenance research, is often crucial to constructing and understanding a provenance.