Pleurisy is inflammation of the pleura, the thin sac surrounding the lungs. It causes chest pain that worsens with breathing or movement. There are two types - dry pleurisy where the inflamed pleura rub together, and wet pleurisy where fluid accumulates in the pleural space. Causes include infections, cancer, autoimmune diseases, trauma, and other medical issues. Diagnosis involves imaging and tests to identify the underlying cause. Treatment focuses on relieving pain and addressing the cause through antibiotics, anti-inflammatories, rest, and draining large fluid accumulations.