Shadow Faces in Fluent

Kjt

I have created a mesh in gambit in which I have a solid zone adjacent to a fluid zone. When I import this mesh to fluent, I get a wall and a wall-shadow between these 2 zones. so now the sequence of the boundary is: solid interior, wall, wall-shadow, liquid interior. What is this wall-shadow zone and why does Fluent create this? Also, what material property should I assign to these zones (wall amd wall-shadow)..solid or liquid?. Any help would be highly appreciated. Thanks