Main body or content of a page is loaded using mosMainBody() function. In this function, Mambo will decide which file should be loaded based on the value of the query string. Typically, every URL will have a query string variable called 'option'. For example:

Normal URL:
http://domain.com/index.php?option=com_contact&Itemid=73

Search engine-friendly URL:
http://domain.com/component/option,com_contact/Itemid,73/

In the above example, Mambo will load the default page of component 'com_contact' which is 'installdir/components/com_contact/contact.php'. What if there is no query string? In that case, Mambo will load the first published item in your main menu. By default, it is 'Home' which is linked to 'frontpage' component.

Fig 6. Default home page

You can set which items to show on the frontpage either by selecting 'Show on Frontpage' when editing a content, or clicking the 'Front Page' icons in the content table.

Fig 7. Show a content item on the frontpage