Covalent Bonding
 

With diagrams like these which show atoms covalently bonded, what do the dotted lines and the triangle shape represent? I know they help in representing the 3 dimentional structure of the molecule, but as to what they exactly mean, can anyone tell me? (Because when I look at it, I cant see a 3D shape since I dont know what the dots/ triangles represent)

They are used to distinguish between the bonds when drawing a 3D structure 8) ...that's what my teacher said when i asked the same question last year.

Various type of line drawings are used to represent structural information derivated from spectroscopic data. In general, the molecules are presented in some kind of perspective drawing, based on the idea that the four substituents of a tetrahedral center can be divided into two pairs, laying in mutually perpendicular planes. Most often the center and two of such substituents(atoms) are shown in the plane of the drawing (i.e. the plane of the drawing surface) and their bonds are depicted as plain lines ( ––– ). Bonds to the other two substituents(atoms) are shown with different symbols. Bonds to atoms above the plane of the drawing (coming out, toward the viewer) are shown with a bold wedge, with the narrow end of the wedge starting at the center. As an alternative bold bonds are occasionally used. Bonds to atoms below the plane (going in, away from the viewer) are shown with hash wedges. There are two separate conventions in use. In the American usage the narrow edge points to the central atom, while in the European convention, the wide edge points to the central atom. As an alternative, a set of short parallel lines is occasionally used. A broken line or an open wedge can also be found in some drawings, but their usage is discouraged.

In case Macak's post is hard to understand, the wedge shows an atom "coming out of the paper" towards you. The dotted line shows an atom "going into the paper" away from you.