You "blink" quickly back and forth between the Material Plane and the Ethereal Plane and look as though you're winking in and out of reality at random. Blink has several effects, as follows.
Physical attacks against you have a 50% miss chance, and the Blind-Fight feat doesn't help opponents, since you're ethereal and not merely invisible. If the attack is capable of striking ethereal creatures, the miss chance is only 20% (for concealment).
If the attacker can see invisible creatures, the miss chance is also only 20%. (For an attacker who can both see and strike ethereal creatures, there is no miss chance.) Likewise, your own attacks have a 20% miss chance, since you sometimes go ethereal just as you are about to strike.
Any individually targeted spell has a 50% chance to fail against you while you're blinking unless your attacker can target invisible, ethereal creatures. Your own spells have a 20% chance to activate just as you go ethereal, in which case they typically do not affect the Material Plane (but they might affect targets on the Ethereal Plane).
While blinking, you take only half damage from area attacks (but full damage from those that extend onto the Ethereal Plane). Although you are only partially visible, you are not considered invisible and targets retain their Dexterity bonus to AC against your attacks. You do receive a +2 bonus on attack rolls made against enemies that cannot see invisible creatures.
You take only half damage from falling, since you fall only while you are material.
While blinking, you can step through (but not see through) solid objects. For each 5 feet of solid material you walk through, there is a 50% chance that you become material. If this occurs, you are shunted off to the nearest open space and take 1d6 points of damage per 5 feet so traveled.
Since you spend about half your time on the Ethereal Plane, you can see and even attack ethereal creatures. You interact with ethereal creatures roughly the same way you interact with material ones.
An ethereal creature can see and hear the Material Plane, but everything looks gray and insubstantial. Sight and hearing on the Material Plane are limited to 60 feet.
Force effects and abjurations affect you normally. Their effects extend onto the Ethereal Plane from the Material Plane, but not vice versa. An ethereal creature can't attack material creatures, and spells you cast while ethereal affect only other ethereal things. Certain material creatures or objects have attacks or effects that work on the Ethereal Plane. Treat other ethereal creatures and objects as material.