A term traditionally used to describe the top portion of a newspaper.

In email or web marketing it means the area of content viewable prior to scrolling. Some people also define above the fold as an ad location at the very top of the screen, but due to banner blindness typical ad locations do not perform as well as ads that are well integrated into content.

If ads look like content they typically perform much better. Google launched a top heavy algorithm to penalize sites with excessive ad placement above the fold.