A Sculpted Prim (or Sculptie) is a Second Life 3D primitive object whose shape is determined by a texture. These textures are called Sculpt Textures or Sculpt Maps. You can use sculpted prims to create more complex, organic shapes that are not currently possible with Second Life's prim system. Sculpted prims work with UV maps. Instead of making an object with a certain, very distinct shape, you take an object with a very generic shape and use the texture file to tell it where to move vertices. That way the poly count stays low and things still look good.