The character becomes ethereal, along with the character's equipment. The character enters a place called the Ethereal Plane, which overlaps the normal, physical, Material Plane.
When the spell expires, the character returns to material existence.
If the character ends the spell and become material while inside a material object (such as a solid wall), the character is shunted off to the nearest open space and take 1d6 points of damage per 5 feet that the character travelled.