How to get Host for Redirect action of Shopify in Laravel

[Magecomp-User]

I am trying to change browser top-level URL in embedded app of shopify. I got the solution for performing this task using Redirect action of shopify using this link  .
This solution is working fine as per my requirement but I am stucked for retrieving host for parameters for createApp(). 
Can anyone have an idea what is exactly host in this action and how can I get the value of the host?
I got this link for retrieving host  but I can't get an exact idea what I have to do exactly

Note: I am using Laravel 8 and osiset/laravel-shopify addon version 17.1 to create an app of shopify. And shopify app type is embedded.

[nafeeur10]

$host = base64_encode("$shop/admin");