Contrast Ratios on TFT monitors

[(Shovel)]

Could someone please tell me what they are and what they affect?
I'm still looking to buy one but a lot of the TFT jargon is new to me.

Is it an important consideration?

 

[Embattle]

Couple of quotes for you:

While largely irrelevant for CRTs, contrast ratio is an important spec for LCDs since the range from lightest to darkest has immediate bearing on LCD image quality. Manufacturers claim LCD contrast ratios ranging from 200-to-1 to 400-to-1, but that ratio is calculated in too many different ways to make any meaningful comparison. Take this specification with a large grain of salt.

A 300-to-1 contrast ratio, indicating the difference between the whitest whites and the blackest blacks, is the minimum for good image quality

 

[(Shovel)]

Thank you.