The puffy taco is defined by a piece of bread that is fried before it is ever shaped, and that order is what makes it itself. A disk of fresh masa is dropped into hot oil raw, where it blisters and balloons into an airy, bubbled shell that is then bent into a taco form while still hot and pliable. A standard taco shell is a pressed tortilla fried flat or curved; the puffy taco is masa that puffs in the oil and is folded around that puff. That blistered, hollow-walled shell, light and crackly rather than dense and brittle, is the whole identity, and the picadillo inside is the filling a shell that dramatic was built to carry.
The craft is a timing problem at the fryer. The masa has to go in fresh and uncooked so steam can inflate it; a dried or pre-cooked tortilla will not puff. It is shaped in the seconds after it comes out of the oil, while it is still soft enough to bend without shattering and firm enough to hold the bend as it cools. The shell ends up structurally strange: airy and crisp but fragile, with thin walls that crack rather than fold, so it is filled lightly and eaten fast before it gives. The picadillo, a seasoned ground beef cooked with potato and a tomato base, is chosen because it is moist enough to season the dry shell from the inside but not so wet that it collapses the puff before the eater gets to it. Shredded lettuce, tomato, and cheese go on as the cool, sharp counter to a hot fried shell and a rich filling, applied in a volume the delicate walls can actually support.
The variations stay tight because the shell dictates so much. The protein swaps to shredded chicken, beans, or guisado while the fried-puffed masa stays fixed; a flat or open build serves the puff without the fold. The puffy taco sits inside the broad American taco, burrito, and wrap family, where a flexible bread folds around a complete meal and the containment, not the filling, is the defining engineering. Each of those traditions is a codified form with its own rules and deserves its own article rather than being crowded in here.