Noise Reduction?

When people say noise reduction, what dot hey mean. ie: Have you tryed any noise reduction programs?

 

i have noise ninja, which is pretty ok, but i dont have a liscensed version, so there are watermarks.

 

You can dowload a free version of 'Neatimage' which works really well and has no watermarks.

Noise is the digital equivalent of film grain. It manifests itself at higher ISOs Sometimes it can add to a picture but most times people just want to get rid of it.