Rhodophyta, commonly known as red algae, are a diverse group of photosynthetic organisms primarily found in marine environments. They are characterized by their reddish color, which comes from the presence of pigments like phycoerythrin. Red algae play a crucial role in marine ecosystems, providing habitat and food for various marine species. These organisms can vary in size from microscopic forms to large seaweeds. Rhodophyta are also important in human use, as they are harvested for food and used in products like agar and carrageenan, which are thickening agents in various food and cosmetic items.