As described in user permissions the majority of control over what particular users can and can't do in the system is controlled by their permissions group on each Project.  The Portfolio account however, like the Admin Account, opens additional features globally by permitting the user to access Portfolio capabilites.

The user will now be able to see and select the portfolios they have permissions to view and any projects within these that they have a read or higher permission on.

The Portfolio account is set with a tick box on the User/Project Permissions form.  Once set the user will be able to: