The birria taco is defined by a step most tacos never take: the tortilla is dragged through fat before it is filled. A corn tortilla is dipped in the rust-red consommé that rises off the braise, fat and chile and all, then laid on a hot griddle so that coating fries into a crisp, stained shell. That fried tortilla is the whole sandwich. It is what separates a birria taco from a stew served with tortillas on the side, and the dip of consommé that comes with it is the same broth closing the loop.
The craft is a frying problem with a braise behind it. The beef is cooked low in dried chiles, vinegar, and spice until it shreds and the surface fat renders into a deep red liquid, which is the consommé and the flavor base of everything. The tortilla is dipped in that fat and griddled until the starch sets stiff and lightly crisped, structural enough to hold a heavy wet filling that an untreated tortilla would not. Melting cheese goes on while the tortilla is still on the heat so it slumps into the meat and glues the fold, and the shredded birria is laid in before the taco is folded closed and pressed until the outside is crisp. The consommé on the side is not a sauce poured over the top; it is a dip the eater controls, so the shell stays crisp until it meets the broth on the eater's terms rather than the kitchen's. The whole thing is built to order and eaten fast, while the fried face still holds against the braise inside it.
The variations are a tight family around the same fried-tortilla, dip-on-the-side move. The quesabirria pushes the cheese forward into a crisped, almost griddled-flat build; the birria ramen and the consommé-soaked rice plate carry the broth past the taco entirely; the goat and chicken versions swap the protein while keeping the dip fixed. These sit inside the broader American taco, burrito, and wrap map, and each deserves its own article rather than being crowded in here.