Contrast is just the amount of color, and brightness of color in the picture.
That is incorrect. Contrast has nothing to do with color, unless we are talking about color contrast, which is a completely different topic.
Contrast is the difference between the lightest and darkest parts of the image, or the shadows and the highlights.
An image with high contrast has very deep shadows, near black, and very bright highlights, near white. There is a huge range between the darkest tone and the lightest tone.
Images with a low contrast will have less of a difference between these tones. Shadows will be grey and not black, and highlights will also be a light grey and not white.
If you are talking about color contrast, or contrasting colors, that is completely different, and refers to the color wheel. Colors which are opposite on the color wheel are contrasting, like cyan to red, or magenta to green, or blue to yellow. Those colors when combined in a photo provide color contrast, no matter what the exposure is, or the difference between shadows and highlights.
Also, to say that low contrast pictures are less attractive is far too general of a statement. Images should be judged on an individual basis.