Blind is an affliction; a negative status effect that handicaps the target.

A creature under the effect of Blind will almost always fail in whatever action they try while they are blinded. They'll fail their spell castings and miss with their weapons. They also can't dodge or parry any physical attacks directed at them while blinded.

Players are able to inflict Blind on a target using the blind spell from the Offensive Affliction Magic skill.

Players can increase their chances of resisting a Blind Affliction spell by wearing jewelry that raises their Desert resistance.

Gingos and Kibans are able to inflict Blind on their enemies by kicking sand in their eyes or spitting ink in their eyes, respectively. Both these effects are not magical and thus Desert resistance will not help you resist it. Creatures that are immune to Blind spells similarly are not immune to these effects.