Cystic fibrosis is caused by a defective CFTR gene that codes for a chloride channel protein. This leads to thick, sticky mucus production throughout the body. The mucus clogs lungs and pancreas, causing chronic infection, inflammation, and organ damage. While treatments aim to clear mucus, fight infection, and improve nutrition, lung disease remains the main cause of mortality. New drugs called CFTR modulators target the defective protein and may transform treatment by improving symptoms and slowing disease progression.