In the James Bond film Live and Let Die (1973), Guy Hamilton, a snake crawls through the bathroom. James Bond is in the bathtub. He does not have any suspicion of the coming danger. We as viewers know a little bit more than the protagonist. At the end of the scene, our lead in knowledge has disappeared: James Bond and the audience are even. In the film Pulp Fiction (1994), Quentin Tarantino, a strange light comes out of a briefcase. We as viewers cannot look inside the briefcase, the main character can. The audience knows less than the protagonist.
In the first example there is tension due to prior knowledge of the viewer. In the second example there is curiosity caused by a lack of information. As a scenario writer you can, at times, make the story more exciting by giving the viewer the lead or putting him behind.