the molecule

If two or more atoms are connected in a covalent way, and neutral particles are mad, than those particles must be molecules.
Mostly we deal then with different atoms, but sometimes with the same atoms.

Something about the threedimensional shape of molecules.
Have a close look at the models below (of molecules):

left could be tetra chloro methane and right di cloro methane.

the cyclic form of glucose

Molecules are built up of two or more connected atoms.
The occupy space and have a threedimensional shape.
You can have extremely simple molecules, like H-H (H2).
This Hydrogen molecule is very small, linear and symmetric.
But most molecules occupy much more space, are bigger, like glucose.