A  pan is where the camera stays in one place (stationary), and is directed to sweep to the left or right.  This is usually used to reveal more information, action, or character.  Usually, the Pan only goes in one direction as it follows a character, or reveals something new in the scene. When a Pan goes from left to right in the same shot, or vice versa,  it is called a Whip Pan. In horror, it can drag out the moment, leaving the audience in anticipation of what is about to be shown.