I mean Mexican food is the authentic stuff. Tex-Mex is more americanized mexican food but still great quality (Chipotle, Qdoba) Taquerias are Mexican restaurants that specialize in Tacos.
If you ever want to try some real authentic Tacos, then be prepared for no dairy products, corn tortillas, a meat topped with white onions and cilantro, with some limes to squeeze over it.
The best common tacos are: -Al Pastor (marinated pork with little bits of pineapple) -Chorizo (spicy ground sausage, tastes best with spicy salsa) -Asada (steak bits, tastes best with lime juice and sauteed onions)
Not sure since I heard some people use milk in their guacamole *shudder*