Contrast Ratio is the ratio of the brightest white a monitor can create compared to its darkest black. Contrast is typically expressed as 500:1 for example, this would mean the monitor's white colors are five hundred times brighter than its black colors. 

What is a Good Monitor Contrast Ratio?

A "good" contrast ratio will depend on your preferences and what you'll use your monitor screen for. Most LCD monitors have a contrast ratio between 1000:1 to 3000:1, and this works fine for everyday tasks like browsing the internet, sending emails, and editing documents. However some more advanced OLED displays can have contrast ratios of up to 100000:1. High contrast ratios like this are great for sharper image detail while gaming, watching films, or editing photos.