Entry in progress—B.P.
 
Wikipedia: Taco
A taco (pronounced /ˈtɑːkoʊ/) 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, mutton, shellfish, vegetables and cheese, allowing for great versatility and variety. A taco is generally eaten without utensils and is often accompanied by a garnish such as salsa and vegetables such as cilantro, tomatoes, onions and lettuce.
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Tacos dorados (fried tacos) called flautas (“flute”, because of the shape), or taquitos, for which the tortillas are filled with pre-cooked shredded chicken, beef or barbacoa, rolled into an elongated cylinder and deep-fried until crisp. They are sometimes cooked in a microwave oven or broiled.
 
Mexconnect
Wrap It Up: A Guide To Mexican Street Tacos - Part 2: Nighttime Tacos
by Karen Hursh Graber
Published on January 1, 2006
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TACOS DORADOS
Also called taquitos or flautas, these differ from other kinds of tacos in that they are rolled around a filling and fried until hard, rather than being made with soft tortillas folded around the filling. Tacos dorados are usually filled with shredded, cooked chicken or beef. They are topped with shredded lettuce, salsa, crema and grated cheese.
 
Rolly’s Mexican Kitchen
Taco vs. Taquito
¿Which is it?
Well, it sort of depends on where you live.  It my part of México, the names tend to be interchangeable, although most people, when pressed, will agree that the things on the left are tacos, while the ones on the right are sometimes called tacos dorados (golden tacos), but more commonly they are taquitos.  In the USA, they are always taquitos.

Confused?  Me too.

Updates:
My friend Esperanza says she only knows them as tacos (left) and taquitos (right), and that tacos dorados are tacos closed with a toothpick and fried golden brown.
 
Dallas Food
The Search for Tacos Dorados
Wednesday, June 10 @ 18:26:02 PDT by Scott
Whenever I sit down at an unfamiliar Mexican restaurant, I scan the menu with the hope of finding tacos dorados—“golden tacos,” so-named because the tortilla or whole taco is fried to the namesake color. Rarely do they appear under that name, outside of restaurants serving primarily Mexican-Americans. Rarely do they appear at all. On to the food…
 
On English menus, tacos dorados are more likely to be called “crispy tacos,” “hard tacos,” “deep-fried tacos,” or even “old-fashioned tacos.” The latter two terms better capture the dish by referring to the cooking method and implicitly acknowledging that it has become something of a throwback.
 
Tacos dorados, like “soft” tacos, originated in Mexico, but have evolved significantly in America through a combination of influences, including ingredient availability, cross-cultural acceptance, and eventually corporate economizing.