ISO sensitivity refers to a camera's ability to capture light. It is a measure of how sensitive the camera's sensor is to light, with higher ISO values allowing for better performance in low-light conditions. However, increasing the ISO can also introduce noise, which may reduce image quality. When adjusting ISO sensitivity, photographers must balance light and noise. A low ISO setting is ideal for bright environments, while a higher setting is useful in darker settings. Understanding how to manipulate ISO sensitivity helps achieve the desired exposure and clarity in photographs.