Some might say that the lifeblood of a taco, the very essence upon which it stands to be judged as the culinary masterpeice it is, lies within the filling. The meats and veggies held within the tortilla shell. Nay!!! For how farest the house built without a foundation. Indeed it shall topple with time. The tortilla is that foundation for the taco!
Generally made from corn (masa) flour or wheat flour combined with water, lard (optionally), and salt, rolled into disks and cooked, either by frying or over stove top, a well made tortilla not only provides a beautiful vessel for delivery of a taco to ones mouth but if made correctly will add much in terms of flavor as well.
Corn tortillas tend to be more flavorful depending on the masa you choose to use but can be more brittle unless fried. Flour tortillas tend to be more elastic due to the gluten development during the kneading process that result in a sturdy tortilla that holds up to more stress but will never get that hard taco crunch.