You've opened up a can of worms. I live in south TX, so Mexican/Tex-Mex food is plentiful to say the least. You cannot just order a taco anywhere without hearing "What kind?" I have some very strict ideas about what constitutes what kind of taco:
Average tacos: Your basic beef, lettuce, tomato, cheese taco. IMO, they go in a hard taco shell only. However, IMO, they are boring and the antithesis of Mexican food. I just simply avoid them as much as I can. This is what most people envision as a "taco."
Breakfast tacos: Something you don't find much outside of south TX, but they generally include an egg (or two) scrambled with your choice of stuff. My favorite are fried potatoes and cheese (I've posted a recipe on here, it's basic). Bacon, refried beans, chorizo, barbacoa, chilaquiles, country sausage, and machacado are all HUGELY popular around here. You can also find non-egg breakfast tacos like bean and bacon. These require tortillas, most commonly flour but I prefer corn because it doesn't contain lard. These are by far my favorite types of tacos.
Puffy tacos: Tacos with a shell that's deep-fried on the spot and forms a puffy shape, as the name implies. Though also fried, they don't even slightly resemble your average taco shell. These come with a large variety of fillings, but I generally avoid them because they're invariably greasy. They're hugely popular here, though.
Other tacos: These include guacamole/avocado tacos, as well as street tacos like carnitas, lengua, carne guisada, tripas, etc. Almost always served in a corn tortilla, though you can request flour.
I excluded gorditas here, but they could be considered a taco as well.
Best way to prepare them? For tortillas, some people put them straight on the gas range, but I prefer a cast iron skillet over medium-high heat; just enough to puff the tortillas without burning them instantly. The tortillas should bubble up and brown unevenly, but never become crispy. Homemade corn tortillas usually only require one tortilla per taco, but store-bought corn are invariably served on double-stacked tortillas at restaurants/roach coaches
For crispy taco shells, a hot even works fine. I usually just hang them from the grates on the oven racks. However, like I said, I rarely use them since I don't like the "average tacos."
YMMV.