Noise is an electronic error which appears as artifact in final picture. It is a result of how the CCD and camera processing system reduce the electronic interferences caused by CCD. The noise is amplified by higher temperature and ISO sensitivity. In new digital cameras the system for noise reduction is added. It is commonly more presented in red and green channel as the CCD's are less sensitive at blue color. The noise is amplified by compression process. Resample of picture to smaller size reduces the noise level. Stuck pixels are also referred as noise.
There are several techniques to reduce image's noise. The noise will be avoided with using sensitivity ISO 100 and ISO 200 with shutter time under 1 second. This will be still cheaper as expensive equipment which has noise cleaning system already included.



Let we look at splitted channels. Here is a small cut of original magnified picture:

Here is a sample of picture taken in low-light condition. The picture clipping is magnified and split into three colors. The noise is more visible in red channel. 

Red channel

Green channel

Blue channel: