SqliteVtabShadowNameCallback
Some virtual table implementations (ex: FTS3, FTS5, and RTREE) make use of real (non-virtual) database tables to store content. For example, when content is inserted into the FTS3 virtual table, the data is ultimately stored in real tables named "%_content", "%_segdir", "%_segments", "%_stat", and "%_docsize" where "%" is the name of the original virtual table. These auxiliary real tables that store content for a virtual table are called "shadow tables". See (1), (2), and (3) for additional information.
The xShadowName method exists to allow SQLite to determine whether a certain real table is in fact a shadow table for a virtual table.