Aging can dramatically improve beef tenderness and flavour. It is a carefully controlled process where beef is held at specific temperature and humidity for a set period of time. Premium beef is aged at least 10 to 14 days. Beef CANNOT be safely aged in a home refrigerator.
Marbling can enhance beef juiciness and flavour. It refers to the amount of fine white flecks of fat that you can see running through the lean beef. The amount of marbling helps determine the grade of beef.
Grading is a quality designation based on several characteristics, including marbling. The top Canadian Grade is Canada Prime, found mainly at fine restaurants. In stores, Canada AAA is the premium grade, with the most marbling, followed by Canada AA and Canada A.
Source: Canada Beef Inc.