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 photographers adjust the ISO setting, they balance light sensitivity with image clarity. A lower ISO is ideal for bright environments, while a higher ISO is useful in darker settings. Understanding ISO sensitivity helps photographers achieve the desired exposure and maintain image quality in various lighting situations.