Open a tin of paint and you're looking at three things mixed together:

Pigment — tiny particles of colour. They give the paint its opacity and hue.

Binder — a polymer (acrylic in water-based paints, alkyd resin in oil-based). This is the actual film that stays on your wall. Once dry, the binder is effectively a thin sheet of flexible plastic.

Solvent — the liquid that makes the whole mixture spreadable. In emulsion it's water. In gloss it's white spirit. The solvent evaporates after application — it has no permanent role.