JSONB is a rewrite of the SQLite JSON functions that, depending on usage patterns, could be several times faster than the original JSON functions. The JSONB rewrite changes the internal-use binary representation of JSON into a contiguous byte array that can read or written as an SQL BLOB. This allows the internal-use representation of JSON to potentially be saved to the database, in place of JSON text, eliminating the overhead of steps 1 and 3. Any JSON function that accepts JSON text as an input will now also accept JSONB binary content for that same parameter.

Source: SQLite Forum: JSONB has landed