ISO is among the most important settings for exposure for digital cameras, along with the aperture and shutter speed.
ISO is an abbreviation for International Organization of Standardization, an organization that oversees various standards across many industries. In addition to the various camera settings, ISO covers the PDF format size, paper dimensions, and many more.
In the context of digital photographic technology, ISO describes the light sensitivity of the sensor of the camera. The typical ISO setting in most modern cameras is ranging from its most sensitive value of 100 to the highest, which is 12,800 or more. In addition to being a factor in determining the exposure, it also impacts the quality of the image.
Images taken using an extremely high ISO setting are typically blurred or unnatural images when compared with photos shot using the lowest ISO. Because of this, it's generally advised to choose low or smaller ISO settings.
Larger or higher ISO values are necessary for instance, to take pictures of fast motions as it lets you increase the shutter rate of your camera. Also, indoor or other photos with less light require the use of a higher ISO setting.