Monsters, Inc.'s main duty is to provide all citizens in Monstropolis with energy in the form of captured screams collected from children. They accomplish this by crossing into the Human World through the closets of children's bedrooms and scaring them to the best of their ability. The screams are then collected in special canisters for use as energy. The amount of capture screams collected is a performance metric and is displayed on the company's leaderboard.
Henry Waternoose convinces Sulley to demonstrate his scare tactic to several onlookers. In the process, Sulley scares Boo. He attempts to win back her trust by showing her that he was only acting earlier.
Sully and Boo sneak around the office in an attempt to find Mike. During their search, Boo uncovers an underground passage, which they follow to find Mike and Randall. Randall is trying to get information from Mike on Boo's whereabouts, so he starts up the Scream Extractor and shows his intentions to use it on Mike. Although it's not clear what the scream extractor does exactly, based on hints from the scene and Mike's reaction, we can determine that it is not used for something positive.