The main ingredient in a traditional Greek tzatziki sauce is yogurt, typically made from strained Greek yogurt. Tzatziki is a refreshing sauce that includes yogurt mixed with grated cucumber, garlic, olive oil, lemon juice, and fresh herbs such as dill or mint. It serves as a cooling condiment often paired with grilled meats, pita bread, or fresh vegetables. The tangy and creamy nature of tzatziki makes it a popular addition to Mediterranean cuisine, helping to balance spicy flavors in various dishes.