Primers are a type of paint used as a preparatory coat on surfaces before applying the final paint layer. They help improve adhesion, ensuring that the topcoat adheres better and lasts longer. Primers can also seal porous surfaces, preventing the final paint from soaking in unevenly. There are different types of primers designed for various surfaces, such as wood, metal, or drywall. Using the right primer can enhance the appearance of the final paint job and may also provide additional benefits, like moisture resistance or stain blocking, depending on the specific product used.