Fiber-reactive dyes are used to dye cellulosic fibers like cotton and linen. They form a strong chemical bond with the fibers, producing vibrant and long-lasting colors that resist fading, washing, and rubbing. The dyeing process involves applying the dye to the fibers, followed by a chemical activator that helps form this bond. It requires careful control of temperature, pH, and other conditions. Fiber-reactive dyes are environmentally friendly, with minimal by-products and energy usage.