Blue cheese or bleu cheese is cheese made with cultures of the mold Penicillium, giving it spots or veins of the mold throughout the cheese, which can vary in color through various shades of blue and green.
Blue cheese is a type of cheese with a fungus called Penicillium added to it. The mold makes patches or veins of it look blue. The cheese can be made from cow's milk, sheep's milk, or goat's milk. Types of it include Roquefort cheese, Stilton cheese, and Gorgonzola cheese. These names should only be used for cheeses that are made in certain areas and are protected by the European Union.
Blue cheese is commonly used in salad dressing, or Salad. It is not commonly used in sandwiches.