The jump scare is aptly named for its ability to make audience members jump from their seats. It uses intense, percussive moments of terror, usually coupled with a jarring sound from the soundtrack to invoke surprise and terror out of its audience.
It typically goes as thus: Hero in a dark room. Something moves menacingly in the corner. Hero turns to go the other way. MR. MONSTER IS RIGHT BEHIND THEM! Cue a screech from the string section and there you have your scare.
Though these types of scares are effective, they don’t usually have the lasting effect that keeps people awake at night for a week. Jump scares cause more surprise and shock than actual terror and dread. Regardless, it is good to have them peppered throughout your script to keep people ill at ease.