A coating is a covering that is applied to the surface of an object, or substrate,  and then a solid coating film or layer are formed on the substrate after the drying process.

In typical applications, the coating film should not be peeled off from the substrate and the purpose of coating film may be decorative, functional, or both.

In some other certain applications, a free stand film can also be made by the coating technology after the wet film is dried and peeled off from the substrate. 

Coatings may be applied as liquids, gases or solids e.g. powder coatings. 

Normally 4 key kinds of ingredient are used for coatings. 1)Binders/Film forming materials/polymers. 2) Additives. 3)Pigments/Toners/Fillers/. 4) Solvents including water.