Concealment

Concealment is a chance that your opponent will miss you. For example, if someone has 50% concealment (from something such as Improved Invisibility), then each hit from your opponent has a 50% chance of missing. Can be partially negated by the feat Blind Fighting, which lets you roll twice if you fail your first concealment check. For example, if your first roll says that you miss due to concealment, you can roll again. So a 50% concealment would only be 25% in reality with Blind Fighting.