What is feeding on demand?

When baby wants. On demand feeding refers to feeding the baby when baby wants as opposed to feeding on a set schedule. In the newborn period, on-demand feeding is usually the best way to feed (with, perhaps, a few caveats to make sure the baby isn't snacking and is getting other needs met - diaper changes, burping, sleep, etc.).
When baby wants. Simply feeding when, how often and how much the baby seems to want.