A flat brush is a type of paintbrush characterized by its wide, flat bristles. It is commonly used in various painting techniques, including acrylic, oil, and watercolor painting. The shape of the brush allows for broad strokes, filling in large areas quickly, and creating sharp lines or edges. Flat brushes come in various sizes, making them versatile tools for artists. They can be used for blending colors, creating textures, or applying washes. Additionally, flat brushes are often favored for their ability to produce clean, defined shapes, making them essential for both beginners and experienced painters alike.