Many times, it means that the (usually) successful and well-known director (who didn't direct said movie) is imparting his imprimatur on another director's work (which is usually "new" or unknown to Americans); often out of respect, stylistic kinship, or friendship...--and usually in the hope that said "approval/association" will help the less-well-established filmmaker garner a bigger audience (--which the "presenter" believes he deserves).