"Contrast" is the difference in color and light between parts of an image.

If all parts of a photograph, be it color or B&W, were completely and equally illuminated, or at the same "brightness" level, nothing would stand out in the image.

There would be no point of interest, no "pop" to the subject, it would appear "flat", which describes a lack of contrast in a picture.

I happen to be a fan of higher contrast photography; but many people prefer less "edge" and a softer effect.

The picture above, depending on how it appears on your computer monitor, is an example of how I like a picture to look, in terms of contrast.

I think that a bit of extra contrast, not overdone to the point where there's no shadow detail, adds a bit of drama to an image.

Check out this excellent article with tips on how to control contrast in digital photography.

Source:www.jimippolito.com