URL Rewrite | Help understand a regular expression logic

Hi,

I am looking in to an existing ARR farm to document the configurations, could some one please help me understand the below conditions-{KBRedirect:{C:1}{HTTP_HOST}/{R:1}?{QUERY_STRING}}

Here is the Rule description-

Rule starts with (.*) with couple of conditions and action is Redirect {C:2}

Condition1:-  {CACHE_URL} matches pattern ^(https?://)

Condition2:- {KBRedirect:{C:1}{HTTP_HOST}/{R:1}?{QUERY_STRING}} matches pattern (.+)

I cant figure out the 2nd condition input. please help.