Final answer:
The space between the lungs in the chest is called the mediastinum, which contains the heart, trachea, and other structures, enveloped by the pleural cavity that holds pleural fluid facilitating lung movement.
Step-by-step explanation:
The space between the lungs in the chest is known as the mediastinum. This central compartment of the thoracic cavity is bordered by the pleura of each lung and contains the heart, trachea, esophagus, and other vital structures. The pleural cavity is a smaller space within the pleura that surrounds each lung and contains pleural fluid, allowing the lungs to move smoothly during breathing.