With this sub-action you are able to fetch the result of a URL, much like the URL commands that Nightbot and many other bots have, provide a URL, and a variable name to write the result to, and you'll be able to use it in other sub-actions.
An example usage, would be a website that just returns a joke. You would enter the URL, and in the variable name, just put
joke, and as as another sub-action after, send a message to your Twitch channel, with the message being
%joke%. Now you have a joke action, that you could trigger by many different means!