Relatively new to Vue, trying to understand `defineEmits`

The post title says it all, but I reading through the Vue documentation and doing the tutorials.

The `defineEmits` functionality through me off a bit since it's not clear to me why you would use `defineEmits` over just having a `prop` that is a function passed down from the parent. Maybe this is my React/Solid brain thinking.

For reference this is the doc I am referring to, though it does appear in the tutorial as well.

- https://vuejs.org/guide/components/events.html#declaring-emitted-events