What are solvents and thinners?
Solvents dissolve a substance in a solid or gaseous state, while diluents dilute the already liquid substance. Solvents can always be diluents. However, thinners do not always dissolve. Water can be e.g.. in dispersion paints only with a thinner, but not a solvent.
What happens when the binder dissolves?
As the binder dissolves, the intermolecular forces in the binder weaken, and the solvent molecules enter between the binder molecules. New intermolecular forces arise between the solvent and binder molecules. This is only possible then, when the solvent and the binder have intermolecular forces of the same order of magnitude. It also explains it, why certain solvents are only suitable for certain binders. Dissolving the binder is a physical process.
What is the difference between proper solvents and latent solvents and non-solvents?
Appropriate solvents dissolve a given substance at room temperature. It is possible, because the intermolecular forces in the solvent are of the same order of magnitude, what the intermolecular forces in the binder.
Latent solvents have a hidden dissolving power, revealing itself only after activation by another substance. Since the intermolecular forces of these solvents differ significantly from the binder forces, then they can dissolve them only then, when some other substance equalizes these forces with the intermolecular forces of the binder.
Non-solvents cannot dissolve the binder. They are used as diluents in order to make the solvent mixture cheaper or to weaken too strong the dissolving power.