A cleavage is the hole left after you cleave something. More commonly though, a cleavage is the space between a woman's breasts.
A college is a place of higher learning, similar to a university.
An edge is a line or border where one thing stops and another thing starts. Edges are very important for finding your way around in the world, and most animals have eyesight designed to detect the edges of things. The picture clearly shows the edge of a building against the sky. A similar word to edge is boundary.
A hedge is a row of plants that have been planted very close together and trimmed into shape. Hedges can be used instead of fences to mark a boundary or to keep animals (or people) from getting over the fence. Hedges are a very simple form of topiary. If you grow a lot of hedges together in a pattern, you can make a hedge maze.
A ledge is similar to a shelf, being fairly narrow and horizontal. Ledges are generally built into a building, either for decoration or for practical reasons, like a windowledge.
A wedge is a triangular shaped piece of something where one end is very pointy and the opposite side is flat. Wedges are designed to be driven into places by hitting the flat end so the point is driven into a gap. Wedges are commonly used for keeping doors open, or for driving into blocks of wood to help split them.