A taco is a traditional Mexican dish composed of a corn or wheat tortilla folded or rolled around a filling. A taco can be made with a variety of fillings, including beef, pork, chicken, seafood, vegetables and cheese, allowing for great versatility and variety. A taco is generally eaten without utensils and is often accompanied by garnishes such as salsa or chili pepper, avocado or guacamole, cilantro (coriander), tomatoes, onions and lettuce. Southern California fish taco. If you haven’t tried them, you simply must.