Scenario: I have a collection of projects (the channel) in a portfolio page (the template), with the title and feature image showing on each. When I click on a project, I want to have a modal box with all information about it - description, gallery of images, client, team members etc (custom fields).
My initial thought was to use AJAX to load the additional information by calling an XML template that accepted the entry id as a GET variable and returned all of the additional information. Then I wondered whether all of this additional information was already loaded in the portfolio template's database call. Are all of these custom channel fields already loaded and simply not displayed?