The primary herb used to make pesto sauce is basil. This aromatic herb imparts a fresh, vibrant flavor to the traditional Italian condiment, which originated in Genoa, Italy. Pesto is typically made by blending fresh basil leaves with garlic, pine nuts, Parmesan cheese, and olive oil until a smooth, paste-like consistency is achieved. Variations exist, with some substituting different nuts or greens, but basil remains central to its identity. Pesto sauce is often enjoyed with pasta, spread on sandwiches, or used as a flavor enhancer in various dishes, making it a beloved staple in Italian cuisine.