Building up suspense without boring the audience is not easy. Whatever is a director to do? Jump scares to the rescue! Everyone knows what a jump scare is. It's the overused horror technique of having a sudden image pop up on screen with an equally sudden, loud noise, usually a loud brass horn, or a woman's scream, emphasizing it. This is considered a cheap shot as far as scares go, because really, the image could be anything and it will still give viewers a rush. But hey, it is guaranteed to work and it's easy, which means this gets used to death and beyond. In a way, jump scares are a close relative of Gorn, because both tend to be used as substitutes for actual suspense.
Unfortunately, even jump scares can be handled poorly. Films often have obvious "safe scenes" where the audience knows nothing interesting will actually happen, and very few horror movies use this predisposition to their advantage, however if they did so regularly, they wouldn't be considered "safe scenes" in the first place. Using too many jump scares will also make them more of a nuisance than a genuine scare.
Cat Scare is a subtrope where the scare itself is false but the jump effect is retained.
When used on its own in a Web Original, it can be known as a screamer or a prank. You know, the videos that encourage you to turn up the stereo and/or examine the picture closely. Related to Shock Site, where the startlement and horror arises from unexpectedly viewing a disturbing image.
See also Chandler's Law
Since jump scares are so prevalent in the horror genre and even outside it, this page will not have any examples.