Beef tacos are not a fixed part of the cow, but many parts of the meat can be cut like this.

Beef tacos are indeed made from beef, and good beef tacos are usually made from the tenderloin of the cow, although other parts can be made into tacos as well. Standard meatloaf is made from the leg of the animal, but the fancier ones are made from the loin, though they are more expensive and not as common, and most markets sell the leg.

Distinguishing:

Many of the poorer quality beef rolls are actually quite good to distinguish, because it is synthetic, so many fat beef cut into slices, you can see the division is very obvious and very regular a lean meat a fat meat between the situation. Because the butter and lean meat is neatly arranged, the fat beef simply can not grow so distinctive fat and lean boundaries.

The more fat boundaries there are, the more minced the meat is. The real natural block of fat cattle fat and lean distribution boundaries are not obvious, look closely at the natural growth, the boundaries are more fuzzy.