https://www.techiediaries.com/react-spread-operator-props-setstate/
https://stackoverflow.com/questions/43484302/what-does-it-mean-rest-in-react-jsx

Well, let's say you have a such route:
<ProtectedRoute path="/private" component={PrivateArea} />

So, when the above component is called, this happens:

line 5:
var Component = PrivateArea
var rest = *remaining properties*
you can add console.log(Component); console.log(rest); between line 5 and 6 to check it

line 8:
'rest' is passed to Route, so ProtectedRoute works as a wrapper for Route component.

line 9: standard rendering routine for Route component
props is an object, which contains Route component attributes, including those, which were passed through 'rest' var.
Add 'console.log(props);' before if-statement.

line 11:
call PrivateArea component (because Component=PrivateArea)

test

test