Why does AI need curves, not lines?

Here are two kinds of dots. One kind is safe. One kind is a threat. A straight line has to cut between them.

A line has one angle. It picks one axis and commits. Real decisions are not that simple.

A curve bends around what it needs to. That bend is what AI does inside. It learns where to curve so the right dots land on the right side.

When someone says a model has "weights" and "layers," what they mean is: a stack of small curves, combined, that together make one big, custom-shaped boundary.