The Portal Site Connection is used to link one site collection with another site collection within SharePoint. Let's suppose, we have a site collection named "site", and you need to provide the link that can configure a portal site connection that navigates to the main site collection called the "Publishing site".
In simple words, suppose you want to move from "site" to "publishing site".
The configuration steps have been provided below:
1. Navigate to Site Settings section
2. Configure the Portal site URL as given below