Where does the update:foo event come from?

Question

Vue.js

I read the following in the documentary:
The following will be converted to:
<comp :foo.sync="bar"></comp>

<comp :foo="bar" @update:foo="val => bar = val"></comp>

In order for the child component to update the value of foo, it must explicitly emit an event, instead of changing the input data parameter: I don’t understand what update:foo is ?? is this a special event in Vue that is called when the input parameter changes? changing the value of the parent? And why is this some strange event with a colon ":"?
this.$emit('update:foo', newValue)

Answer 1

This is the name of the event, you can either updateBaz or helloWorld to call it.
As for the colon, it's kind of like a namespace. Vue in this case generates the name of the event itself.
According to the documentation
will be converted to
Etc.