What is Portal Site Connection?
Site Connection URL: http://k2/
Subsites:
http://k2/one/
http://k2/two/
http://k2/ ---Site Settings--Site Collection Administration--Site Heirarchy

When a new subsite is created, a link is by default created on Top Link Bar.
When a new site collection is created under http://k2/ site collection, there is no link created on Top Link Bar.
Create a new site collection:CollectionOne with URL http://k2/sites/CollectionOne/
Open the site collection http://k2/
Site Settings--Look and Feel--Top Link Bar

New Navigation Link


When you are in http://k2/sites/CollectionOne and want to go to http://k2/ site collection, there is no link.

To create a link to http://k2/,
Site Settings--Site Collection Administration--Portal Site Connection


Similarly, a web application http://k2:8189/ with site collection: Project8189 is created. You can create a portal site connection to http://k2/.
