Basically ISO is a light censor in your camera. It measures the sensitivity of the light absorbed into your camera. The idea how it works is very simple. The higher the number the more bright picture you will get.
- ISO 100: Quite neutral light sensitivity.
- ISO 3200: Very bright picture.
As a tip, I can tell you that most photographers will not advise you to use high ISO. If you increase the number too much the picture might loose some qualities( you will get some grain on it.) Try to play with aperture and shutter speed first (keep your ISO low) and if nothing works, only then... increase your ISO. However, the fact that grain will appear on your picture can also be seen as a creative factor in your photography.
Here is an example of the picture with quite high ISO number (ISO 800)
Here is an example of the picture with quite high ISO number (ISO 800)
