The broad definition of Tallow is rendered beef fat. But not all beef fat is created equal. The highest quality Tallow comes from suet. A firm, dense fat surrounding the kidneys and other organs, rather than the soft intermuscular fat found around and between the muscles (the marbling you see in a steak). Suet is fundamentally different from that muscle fat: it has a higher melting point, a cleaner and more neutral flavour, a longer shelf life at room temperature, and a different fatty acid composition altogether. That distinction is why "Tallow" traditionally referred to rendered suet.
To render it properly, the raw suet is slowly boiled, then spun in a centrifuge to separate out any remaining liquid or connective tissue. What's left is pure, single ingredient Tallow that turns solid and pale at room temperature and melts quickly with heat, no additives, no processing aids, no seed oil hiding in the ingredient list.
Beretta Farms' Grass Fed Beef Tallow is rendered exactly this way, using 100% kidney suet from Canadian RWA cattle, raised without antibiotics, hormones, or steroids. We also render Bison suet the same way; since bison is naturally leaner than cattle, the resulting tallow is bolder and more nutrient dense, though it behaves the same in a pan.