The term 'CENTER NUT' refers to four different types of nuts: BETEL, PECAN, Kola, and Tree. BETEL is a type of nut native to India and Southeast Asia, and is often chewed as a stimulant. PECAN is a type of nut native to North America, and is commonly used in baking. Kola is a type of nut native to West Africa, and is used to make a variety of beverages. Tree is a type of nut native to South America, and is often used in cooking. All four of these nuts are considered to be center nuts because they are all found in the center of their respective trees.