Suspense is the feeling of uncertainty or unrest of the outcome of an event or action which is to happen in the nearby future. This oftens is often referred to in cinematic/dramatic work; used usually while watching thrillers or horror. It is usually used in thrillers as a way of adding suspense and curiousity to the viewers state of mind. Directors and producers used this as a way to cause strain and unrest to the viewer as they sit in their seat wondering where the current events would lead to. Suspense is usually used to lead up to a big/important scene which increases excitement.
Alfred Hitchcock was a huge user of supsense and often described it as adding mystery to the affairs in the film. Although adding suspense seems like a simple process it, varies on the age group and audience.