A foundation brush is a makeup brush that is specifically designed to apply liquid or cream-based foundations onto the skin. The bristles on this type of brush are typically flat and dense, which allows for an even distribution of product across the face. Foundation brushes come in various shapes and sizes, with some being more suitable for specific areas of the face such as the forehead or cheeks. By using a foundation brush, it is possible to achieve a flawless, airbrushed finish when applying makeup.