Sweet Basil: big and dark green leaves, wonderful fragrance and flavor, the key ingredient of pesto.
Purple Basil: leaves purple, coppery glow. It has a clove-like, slightly spicy flavor. It is used in Thai and Vietnamese dishes
Cinnamon Basil: green leaves smaller, less green than sweet basil. The leaves have a spicy-cinammon like aroma. Its stem is cinnamon color. It goes well with fruit. It is used in Asian and Indian dishes.
Keep basil in water, like a bouquet of fresh flowers, and at room temperature. The cold air of the refrigerator will make the leaves turn black.