A base coat is a type of paint or polish applied as the first layer on a surface. Its primary purpose is to create a smooth foundation for subsequent layers, enhancing adhesion and durability. In nail care, a base coat helps protect the natural nail from staining and improves the longevity of the polish. In the context of automotive painting, a base coat provides color and is often followed by a clear coat for added protection and shine. Base coats can come in various finishes, including matte, satin, and glossy, depending on the desired final appearance of the surface.