Miss chance is an effect that causes a creature's attacks to miss a certain percent of the time. Like concealment, miss chance is calculated before each attack independent of the attack roll. However, miss chance does not stack with concealment, rather the higher of the two percentages is used. Miss chance is often used within effects like blindness (granting a 50% miss chance) and rarely ever occurs by itself (e.g. chaos shield). The blind fight feat negates all forms of miss chance.
Like concealment, miss chance can be limited to only melee or only ranged attacks. The melee limitation includes all touch attacks as well as standard melee attacks, while the ranged limitation just applies to standard ranged attacks.