19  ISO (sensitivity) in the Coolpix 700 / 800 / 900/ 950 / 990

In a film camera, sensitivity is a characteristic of the film, not the camera. Film sensitivity determines the amount of light required to produce a given level of exposure: the camera only needs to know the sensitivity of the film in use, and to then adjust the exposure calculation accordingly.

High sensitivity film allows the camera to shoot with  a faster shutter speed, or smaller aperture for a given lighting level.

Higher sensitivity is achieved by altering the chemical composition of the film and results in the appearance of a random pattern called "grain" which can be seen superimposed on image.
Sensitivity in Digital photography has the same effect: higher sensitivity allows higher shutter speeds, at the expense of  noise (the digital equivalent of  film grain)   appearing in the image. Higher sensitivity is achieved by increasing the amplification of the electrical signal from the CCD (sensor) in the camera.

The Coolpix cameras have a standard default sensitivity of  between ISO 64 and 100, depending on the model. This can be altered manually on the Coolpix  800, 950 and 990 models to 100, 200 or 400.

In addition, in low light conditions these camera models will automatically increase the sensitivity (Coolpix 950 firmware 1.2 or later) to allow the camera to increase the shutter speed to as high as possible so that use of the flash is not necessary.