Marbling refers to the white flecks and streaks of fat within the lean sections of meat. It is crucial in a high-quality steak as it contributes to the flavor, juiciness, and tenderness of the meat when cooked. Marbling is a sign of a well-fed animal and is a key characteristic in grading the quality of beef. Steaks with higher marbling usually command a higher price and are considered more luxurious.