system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly are “instincts” and how do they work?

I mean, I know what they do. But what are they? Inherited memories? Where is the knowledge stored and how? Do we even know?
gpt
It's basically any innate behaviour an organism has and it can be both innate (you're born with it) or learned.

For example human babies have a number of very clear instincts they're born with. The rooting reflex causes a baby to go rooting around for their mother's nipple and start suckling. If you gently stroke the side of a baby's mouth, they'll try move towards your finger tip and suckle it.

Human babies are born with a number of other instincts, like immediately holding their breath if you dip them in water or spreading their limbs and grasping if you tip them backwards.

Humans also have learned instincts. For example both societal and family dynamics generally make sure that you instinctively aren't inclined to pursue incestuous relationships. You don't have to be explicitly told. A lot of the cultural habits and traditions of a community will become part of your behaviour over time.

The strongest instincts are the innate one that evolution enforces, ie the stuff animals automatically do because the ones that didn't died without passing on their genes. But on the whole instincts are both learned and innate.