Joint compound is a thick paste used in construction and home improvement to finish drywall seams and repair imperfections. It helps create a smooth surface for painting or wallpapering. Joint compound is typically made from gypsum dust mixed with water and other additives. There are different types of joint compound, including taping compound, which is used for embedding drywall tape, and finishing compound, which provides a smooth final coat. It dries hard and can be sanded down for a flawless finish. Proper application is essential for achieving a professional look in drywall projects.