Tension

There are many forms of tension in movies, but tension always creates anticipation and anxiety about what is going to happen next. Tension is what makes you turn the page. Tension keeps the audience in their seats.

Tension is created when the audience can imagine and anticipate what might happen next in the story, sequence, or scene, but isn't sure which way it will go. The story elements suggest several possible futures. 

We (the audience) HOPE for one outcome(s), but we FEAR another.

More specific forms of tension include dramatic tension, comic tension, romantic tension, suspense/fear tension, and more generally dramatic tension. In all cases, the writer leads the reader/audience to imagine something funny, romantic, or scary is about to happen next.

More importantly, while we can imagine (hope) for a good outcome we can also imagine (fear) a bad outcome, and it is not clear to us which way it's going to go.

In general, tension rises (i.e. the stake rise) when the possible good outcome gets better and/or the possible bad outcome gets worse. Likewise, if we have no sense of the future or if we feel like we know how things will turn out, the tension dissolves. To engage the audience, we must keep the tension high.