Slide 28 of this presentation quotes Rabbi Avraham Fischer of the OU:
Chelev refers to the outer layer of fat called suet. The prohibited chelev is the abdominal fat on the stomach, kidney, and
flank. It can be peeled away like a skin. The rest of the fat which is
permissible is called shuman.
Chelev or Suet is used in occasional cooking (non kosher, obviously) such as French fries. It is also used for making tallow which is still used in some candle products. Suet was also sometimes used as engine lubricant, years ago. In some places, it is also used as a salve for sore skins and blisters. (Perhaps, @Shokhet can comment on what happens to the chelev that is removed by butchers - is it sold for such commercial use?)
As to an answer to the title of the question - according to most nutritionists I've spoken to, only Omega 3 fats are the ones you're "supposed" to eat. Kishke is not one of them, BTW :-P