The pleural space is a thin, fluid-filled area between the two layers of the pleura, which are membranes surrounding the lungs. This space helps reduce friction as the lungs expand and contract during breathing. It also plays a role in keeping the lungs inflated by creating a pressure difference between the pleural space and the outside atmosphere. When the pleural space is affected by conditions like pleurisy or pleural effusion, it can lead to pain and difficulty breathing. In pleurisy, the membranes become inflamed, while pleural effusion involves excess fluid accumulation. Both conditions can disrupt normal lung function and require medical attention.