Dodge Chance Increase is a bonus featured on some items, the amount indicated is the percent added to your chances to dodge an incoming attack.

Remember that the dodge chance is added multiplicatively to the base chance to be hit, meaning that if (considering the attack skills of your enemy and your defensive skills) an enemy would hit you with a probability of 20%, having 50% dodge reduces that to 10%

Ideally with 100% dodge you wouldn't be able to be hit.