Taco fillings are tantalizing, no doubt, but sometimes, keeping track of what's what is challenging. Consider this a cheat sheet. Quoted material comes from Planet Taco: A Global History of Mexican Food by Jeffrey M. Pilcher.
Barbacoa – “Pit-roasted meat. Barbacoa de cabeza de vaca, the entire head of a cow, was a festival dish of the borderlands. Today, barbacoa is often prepared in stainless steel containers.” Whether a pit is involved at most restaurants is anybody's guess. Many recipes for beef barbacoa call for steaming or oven-roasting the meat.
Carne adobada – “Meat marinated in chile paste, a specialty of New Mexico.”
Carne asada – “Grilled meat, a common dish of northern Mexico.” Carne means meat, but often, carne asada refers to beef.
Carnitas – “Bits of fried meat, particularly pork.”
Chorizo – “Sausage spiced with chile peppers.”
Tacos al carbon – “(grilled tacos) began to appear in upscale restaurants in the 1960s with fancy meats such as bifstek (steak) and chuleta (pork chops).”
Tacos al pastor – “introduced by second-generation Lebanese Mexicans, who adapted lamb gyros (also known as tacos arabes) to Mexican ingredients, preparing chile-flavored pork on a vertical rotisserie served with pineapple.”