ISO is short for International Organization of Standardization, an organization that monitors different standards across a multitude of industries. Next to different camera settings, this also includes PDF format standards, paper sizes, and more.
When talking about digital photography, ISO describes the light sensitivity of the camera’s sensor. Typically, the ISO setting provided in most modern cameras ranges from its lowest sensitivity value of 100 to the highest with 12,800 or even higher. Next to playing a part when it comes to exposure, it also affects the visual quality of an image. Photos taken with a high ISO setting typically result in noisy or grainy pictures, compared to photos taken with a low ISO. Due to this, it’s typically advised to use low or small ISO settings.
High or bigger ISO values are needed, for example, to capture rapid movements as it allows you to increase the shutter speed of the camera. Likewise, indoor and other shots with darker lighting may require a higher ISO setting.