Samsung NX1000 User Manual page 61

The ISO sensitivity value represents the sensitivity of camera to light.
Examples
The larger the ISO value, the more sensitive the camera is to light.
Consequently, by selecting a higher ISO sensitivity value, you can
capture photos in dim or dark places at faster shutter speeds. However,
this may increase electronic noise and result in a grainy photo.
ISO 100 ISO400
ISO800 ISO 3200