The size of a camera's sensor plays a crucial role in its image quality. Smaller sensors, often found in smartphones and inexpensive cameras, have cramped pixels that result in noisier images, especially in low light. Larger sensors, on the other hand, produce better photos and videos but come at a higher cost and a bulkier size. The lens's focal length can also be affected by sensor size, with smaller sensors causing a "crop factor" that narrows the lens's effective focal length. When choosing a camera, it's essential to consider the balance between sensor size, cost, and your specific needs and uses.