Contrast is the difference between the black and the white areas on the TV. If a TV has a low contrast ratio then that means that this TV does not have very dark blacks in comparison to the brightness of the whites. A high contrast ratio means that the screen has very deep dark blacks as well as very bright whites. For instance a TV with 50,000:1 is better than one with only 10,000:1. Typically plasma TVs have more contrast than other types of TV. LED LCDs are good for the daytime with great brightness, and although not as bright as other TVs the contrast ratio is still pretty good.