Molecules are composed of more than one atom. The number of atoms that make up a molecule can range from two for the simplest molecule to even in the thousands. The atoms that make up a molecule are bound to each other either by an ionic bond or a covalent bond.
Ions are atoms that have either gained one or more extra electrons which completes their electron shell or lost one or more for the same reason. In the first case the ion is negatively charged and in the second it is positively charged.
Lattices are structures created by the forces of attraction between particles. Lattices can be made of atoms or molecules. Their properties depend on the particles that make up the lattice how they are arranged.
Compounds are formed by the combination of two or more atoms.
Discrete molecules are molecules that do not form a lattice and the low intermolecular forces allow them to remain independent entities.