Resin is a sap released by many types of plants, especially by coniferous species. This sap usually freezes, slowly or immediately, and forms a hard mass and transparent. People use resins mainly as varnishes and adhesives.
More broadly, the term “resin” also includes many synthetic substances of the same mechanical nature (thick liquids which harden into transparent solids).
The word “resin” has been applied in the modern world to almost all components of a liquid which, when applied to hard lacquer or enamel-like finished goods. An example is nail polish, clear coat.