What different "$is_args$args" and "$query_string" ?

Hi guys.

$is_args$args
and
$query_string
is same?

#patter 1
location ~ ^/test/enter1.html {
rewrite (.*) http://another.com/test/list1.html$is_args$args;
}

#patten 2
location ~ ^/test/enter2.html {
rewrite (.*) http://another.com/test/list2.html$query_string;
}

I tried
/test/enter1.html?page=10
/test/enter2.html?page=10

pat.1 -> list1.html?page=10?page=10
pat.2 -> list2.html?page=10

I think same
Am I misunderstanding?