>>>RGB stands for Red Green Blue
>>>The intensity of each is on a 256 point scale (0 - 255).
>>>So red is turned up to 61, green to 89 and blue to 171.
That is how your digital camera works.
For each "pixel" on your camera it measures the strength of the red, green and blue and displays the colour accordingly.
The "mix" of red, green and blue defines what colour that pixel is.
And it does that for every pixel in a picture, thus making up your colour image.
Simple.