[Frank Whiton]

Hi stoneflynymph,

ISO stands for the International Organization of Standardization or ISO. In film cameras it is a measurement of the film's speed or sensitivity to light as measured by the ISO. There is a different rating for digital cameras. ISO also measure other standards and they may show up in many places.

So according to where you came across ISO has a lot to do with how it applies. The most common association of ISO is with film speeds.

Frank