The most commonly accepted theory is that tacos originated in the state of Oaxaca, Mexico, where they were originally made with corn tortillas and filled with various ingredients such as beans, meat, and vegetables.

The original tacos were called "tacos de guisado", which means "stew tacos" in Spanish. They were made with a corn tortilla filled with a stew made from meat, vegetables, and spices.

Tacos became popular in Mexico in the 19th century, when they were adopted by the Mexican army as a quick and easy meal. They quickly spread throughout the country and became a staple of Mexican cuisine.

The most popular type of taco in Mexico is "tacos al pastor", which are made with marinated pork that is cooked on a vertical spit. They are typically served with pineapple, onions, and cilantro.

Tacos can be filled with a variety of ingredients, including beef, chicken, pork, fish, and vegetables. Some of the most popular fillings include carnitas (braised pork), al pastor (marinated pork), barbacoa (stewed beef), and guisado (stew).

Tacos can be topped with a variety of ingredients, including lettuce, tomatoes, onions, cilantro, and salsa. Other popular toppings include guacamole, sour cream, and cheese.

In the United States, tacos have been adapted to local tastes and preferences. American tacos are typically made with ground beef, cheddar cheese, lettuce, tomatoes, and sour cream.

Tacos are typically made with corn tortillas, while burritos are made with flour tortillas. Tacos are typically smaller than burritos and are typically served open-faced, while burritos are served closed.

Tacos are made with corn tortillas, while tostadas are made with fried corn tortillas. Tacos are typically filled with meat, while tostadas are typically topped with beans, cheese, and vegetables. Tacos are typically served open-faced, while tostadas are served flat.

Tacos are made with corn tortillas, while quesadillas are made with flour tortillas. Tacos are typically filled with meat, while quesadillas are typically filled with cheese. Tacos are typically served open-faced, while quesadillas are served folded.

Tacos are made with corn tortillas, while flautas are made with fried corn tortillas. Tacos are typically filled with meat, while flautas are typically filled with cheese or beans. Tacos are typically served open-faced, while flautas are served rolled up.

Tacos are made with corn tortillas, while gorditas are made with a thick corn tortilla. Tacos are typically filled with meat, while gorditas are typically filled with beans, cheese, or potatoes. Tacos are typically served open-faced, while gorditas are served folded.

Tacos are made with corn tortillas, while sopes are made with a thick corn tortilla that is fried. Tacos are typically filled with meat, while sopes are typically topped with beans, cheese, and vegetables. Tacos are typically served open-faced, while sopes are served flat.

Tacos are made with corn tortillas, while huaraches are made with a thick corn tortilla that is shaped like a sandal. Tacos are typically filled with meat, while huaraches are typically topped with beans, cheese, and vegetables. Tacos are typically served open-faced, while huaraches are served folded.

Tacos are made with corn tortillas, while mulitas are made with two corn tortillas. Tacos are typically filled with meat, while mulitas are typically filled with cheese and beans. Tacos are typically served open-faced, while mulitas are served folded.