ODB++ is a manufacturing database much like Gerber that includes: aperture lists, netlists, test files, etc. This "database" is read into Valor Enterprise (CAM) as a "true" representation of your layout database. Valor can supply the scripts that will generate an ODB++ format database for you. The ODB++ format is NOT proprietary, so other tools can generate ODB++ also!
If your fabricator requests a format other than ODB++ [or insists on Gerber], you should find another supplier.
Gerber[R] Data (File). Used in directing a photoplotter during printed circuit board and stencil artwork fabrication. Gerber Scientific Instrument Company used to be the dominant producer of the photoplotters used for "shooting" film, back when mechanical vector type plotting was the only way to get accurate film masters. Their proprietary format for these files became an industry standard.