I'm confused! How can you "see" noise? Or am I being daft? I know sweet FA about cameras although I wish I did!

I was going to make a sarcastic comment about "noise" before

But this is noise....

Good example Adam.

http://en.wikipedia.org/wiki/Image_noise
In short it's the fuzzy/grain effect you get when you use higher iso's. Iso is how sensitive the sensor is too light. It's an artifical system and the drawback is noise.

You can see it in the background of that image when viewed large.
http://www.flickr.com/photos/micky_photography/5468516904/sizes/o/in/photostream/