A chest tube is used to drain air, blood, fluid, or pus from the pleural space (the area between the lung and chest wall) to help the lung re-expand and restore normal breathing. It is a necessary treatment for conditions like pneumothorax (collapsed lung), hemothorax (blood in the chest), pleural effusion (excess fluid), and empyema (pus). The tube is inserted through the chest wall and connected to a drainage system to allow for continuous removal of the unwanted material.