Tallow is a rendered form of beef or mutton suet, primarily made up of triglycerides.
Tallow made by rendering calf suet
An 1883 ad soliciting tallow from butchers and graziers for soap production in the Hawaii newspaper The Daily Bulletin
A tallow candle
Suet is the raw, hard fat of beef, lamb or mutton found around the loins and kidneys.
Calf suet
Tallow after rendering
Red-breasted nuthatch feeding on suet