Suspense leaves unaswered questions in the minds of the audience. The audience are desperate to know what happens next.
Suspense builds up tension.
Sometimes, the audience know more than the characters on screen know. Example is in "The Bomb Theory".
Suspense helps to create drama.
Suspense foreshadows future events.
Suspense makes the audience to sit on the edge of their seat. It also makes the audience scream in terror, increase in heart rate - Visceral Effect.
Suspense can be created through the use of False Plateau. This is when tension is created because something is about to happen but it turns out to be fake, then the atmosphere is relaxed then suddenly the real thing comes on. An Example is in Jaws, when everyone at the beach taught that a shark was approaching but it later turned out to be kids, everone was calm but later the real thing came along.False Plateau lulls the audience into a false sense of security.