Resin is a hydrocarbon secretion that comes from many different types of plants. It also comes from many types of coniferous trees, like pine trees.
Most resin is a translucent yellow or brown color that can be semisolid or solid, and is viscous. It is used in things such as varnish, ink, lacquer, plastic and adhesives. Generally, resins are insoluble in water. Although resin is most often used in its natural form, synthetic resins are also popular, and make the base for things like epoxies, polyesters and silicone.
Natural resin that comes from trees is extracted as a liquid. Sap, mucilage and latex are all forms of resins. Resin, whether natural or synthetic, usually dries to a hard, transparent or opaque consistency.
Resins have been around for thousands of years and have served many different purposes. Frankincense and myrrh were resins, and many of these substances were used for medicinal purposes, food glazing agents and adhesives. Many types of incense were made from resins, and specific resins were used for religious ceremonies.
Some resins walk a fine line between natural and synthetic. For example, nail polish is considered a resin that is organic, but doesn't come from plants.