A high needs baby is a baby who needs a lot more attention from their mother or other parent and cannot be left alone for too long.
A high needs baby usually constantly wants the parents to either hold them, rock them and get agitated more easily when the parent leaves them alone in their crib, bassinet, swing etc.
When you have a high needs baby the high needs baby will become agitated, tense, and cry incessantly until they're picked up.
Also high needs babies are almost always usually always moving around, whether they're being held or sitting in a playpen.
The high needs baby might also move frequently in their sleep.