albums/singles/EP’s released by record companies in marketing purposes. Delivered for free (or at reduced prices) to music journalists, reviewers, radio stations, djs and so on… Sometimes some of the copies are sold on specially organized auctions on a “first come – first served” basis.
In case of white label promos, we are dealing with unfinished works, which are still in production process and at this stage no record label signs its name under such track.