These are early DVD or BD releases of the theatrical version of a film, typically sent to movie reviewers, Academy members, and executives for review purposes. A screener normally has a message overlaid on its picture, with wording similar to: "The film you are watching is a promotional copy, if you purchased this film at a retail store please contact 1-800-NO-COPIES to report it." Apart from this, some movie studios release their screeners with a number of scenes of varying duration shown in black-and-white. Aside from this message, and the occasional B&W scenes, screeners are normally of only slightly lower quality than a retail DVD-Rip, due to the smaller investment in DVD mastering for the limited run. Some screener rips with the overlay message get cropped to remove the message and get released misslabled as DVD-Rips.
Note: Screeners make a small exception here, since the content may differ from a retail version, it can be considered as lower quality than a DVD-Rip (even if the screener in question was sourced from a DVD).
