One thing that jumps right out to people studying the NEC is that Article 215 is  very short. This is surprising to people who've just studied Article 210, Branch Circuits, and are moving on to the next logical step.

You might be thinking feeders are just a heavy version of branch circuits, so Article 215 should just be Article 210 on steroids. But, don't think that way because "it aint so."

Article 210 covers many permutations of branch circuits, and devotes extensive text to dwelling area branch circuits. Dwelling areas don’t have feeder circuits.

Here’s an object lesson in the value of Article 100. Go there now and review the definitions of branch circuit and feeder circuit. Once you’ve done that, you will understand why Article 215 is so much shorter than Article 210.